研究者データベース

研究者情報

マスター

アカウント(マスター)

  • 氏名

    伊藤 肇(イトウ ハジメ), イトウ ハジメ

所属(マスター)

  • 工学研究院 応用化学部門 有機工業化学分野

所属(マスター)

  • 工学研究院 応用化学部門 有機工業化学分野

独自項目

syllabus

  • 2020, 超分子化学, Supramolecular Chemistry, 修士課程, 総合化学院, ホストーゲスト化学、分子間相互作用、水素結合、大環状化合物、イオン認識、構造、立体化学、キラリティー
  • 2020, 分子化学A(有機金属化学), Molecular Chemistry A (Organometallic Chemistry), 修士課程, 総合化学院, 有機金属化学 有機合成触媒 反応設計 有機金属反応機構 有機金属錯体の構造 有機合成化学 触媒化学
  • 2020, 実践的計算化学, Practical Computational Chemistry, 修士課程, 総合化学院, 計算化学、理論化学、分子軌道法、密度汎関数法
  • 2020, 大学院共通授業科目(一般科目):自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, 基礎有機化学、構造有機化学、反応有機化学、有機金属化学、有機合成化学、高分子化学
  • 2020, 有機化学特論, Special Lecture on Organic Chemistry, 修士課程, 総合化学院, 基礎有機化学、構造有機化学、反応有機化学、有機金属化学、有機合成化学、高分子化学
  • 2020, 有機化学Ⅰ, Organic Chemistry I, 学士課程, 工学部, 有機化学 アルカン アルケン アルキン 立体化学 
  • 2020, 物質変換工学, Applied Chemistry and Biochemistry, 学士課程, 工学部, 有機合成,有機材料,化学プロセス,反応器設計,生体材料,高分子材料,分子機能,無機材料,複合材料,電子材料,光機能材料

PositionHistory

  • 創成研究機構化学反応創成研究拠点副拠点長, 2018年10月23日, 2022年3月31日

researchmap

プロフィール情報

所属

  • 北海道大学 化学反応創成拠点(WPI-ICReDD), 副拠点長
  • JST CREST 革新的合成, 研究代表者

学位

  • 博士(工学)(京都大学)

プロフィール情報

  • 公開用メールアドレス

    hajitoeng.hokudai.ac.jp
  • 伊藤, イトウ
  • 肇, ハジメ
  • ID各種

    200901005275827185

対象リソース

所属

  • 北海道大学 化学反応創成拠点(WPI-ICReDD), 副拠点長
  • JST CREST 革新的合成, 研究代表者

業績リスト

研究キーワード

  • メカノケミカル合成   銅(I)触媒によるホウ素化   メカノクロミズム   発光性金属錯体   有機金属化合物   有機金属   organometallics   

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 電子デバイス、電子機器
  • ライフサイエンス / 生物有機化学
  • ナノテク・材料 / 構造有機化学、物理有機化学
  • ナノテク・材料 / 有機合成化学

経歴

  • 2010年10月 - 現在 北海道大学大学院 工学研究院応用化学部門教授 教授
  • 2002年04月 - 2010年09月 北海道大学大学院 理学研究科化学専攻 助教授
  • 2001年04月 - 2002年03月 米国スクリプス研究所 客員研究員
  • 1999年04月 - 2001年03月 岡崎国立共同研究機構分子科学研究所 助手
  • 1996年04月 - 1999年03月 筑波大学 化学系 助手

学歴

  •         - 1996年03月   京都大学大学院   工学研究科   博士課程 修了
  •         - 1991年03月   京都大学   工学部   合成化学科 卒業

受賞

  • 2015年 永瀬財団 長瀬研究振興賞
     
    受賞者: 伊藤 肇
  • 2014年 日本化学会学術賞
     
    受賞者: 伊藤 肇
  • 2011年 北海道大学研究総長賞
     
    受賞者: 伊藤 肇
  • 2008年 有機合成化学奨励賞

論文

  • Rempei Ando, Mingoo Jin, Hajime Ito
    CRYSTENGCOMM 2021年08月 
    Charge-transfer (CT) crystals bearing segregated domains between the electron donor and acceptor molecules are a promising platform for developing new organic functional solid-state materials. However, there is limited diversity in the segregated structures of CT crystals. Herein, we report a novel structure of a CT crystal using hexaarylbenzene (HAB) and tetracyanoquinodimethane (TCNQ) as the electron donors and acceptors, respectively. Single-crystal X-ray diffraction (XRD) studies revealed that hexapyridylbenzene and TCNQ form a segregated layer in crystalline media, and the CT feature of TCNQ was observed in terms of the observed chemical bond lengths in the crystal.
  • Takashi Yanase, Hirohiko Tanoguchi, Nobuhiko Sakai, Mingoo Jin, Ichiro Yamane, Masaki Kato, Hajime Ito, Taro Nagahama, Toshihiro Shimada
    Crystal Growth & Design 2021年07月20日 [査読有り]
  • Koji Kubota, Naoki Toyoshima, Daiyo Miura, Julong Jiang, Satoshi Maeda, Mingoo Jin, Hajime Ito
    Angewandte Chemie 133 29 16139 - 16144 2021年07月12日 [査読有り]
  • Koji Kubota, Naoki Toyoshima, Daiyo Miura, Julong Jiang, Satoshi Maeda, Mingoo Jin, Hajime Ito
    Angewandte Chemie International Edition 60 29 16003 - 16008 2021年07月12日 [査読有り]
  • Koji Kubota, Daiyo Miura, Takumi Takeuchi, Shun Osaki, Hajime Ito
    ACS Catalysis 7956 - 7956 2021年07月02日 [査読有り]
  • Hiroaki Iwamoto, Yu Ozawa, Yuta Takenouchi, Tsuneo Imamoto, Hajime Ito
    Journal of the American Chemical Society 2021年05月05日 [査読有り]
  • Tamae Seo, Naoki Toyoshima, Koji Kubota, Hajime Ito
    Journal of the American Chemical Society 2021年04月28日 [査読有り]
  • Kenta Kato, Tomohiro Seki, Hajime Ito
    Inorganic Chemistry 2021年04月22日 [査読有り]
  • Sota Akiyama, Natsuki Oyama, Tsubura Endo, Koji Kubota, Hajime Ito
    Journal of the American Chemical Society 143 13 5260 - 5268 2021年04月07日 [査読有り]
  • Mingoo Jin, Rempei Ando, Marcus J. Jellen, Miguel A. Garcia-Garibay, Hajime Ito
    Journal of the American Chemical Society 2021年01月20日 [査読有り]
     
    In crystalline solids, molecules generally have limited mobility due to their densely packed environment. However, structural information at the molecular level may be used to design amphidynamic crystals with rotating elements linked to rigid, lattice-forming parts, which may lead to molecular rotary motions and changes in conformation that determine the physical properties of the solid-state materials. Here, we report a novel design of emissive crystalline molecular rotors with a central pyrazine rotator connected by implanted transition metals (Cu or Au) to a readily accessible enclosure formed by two N-heterocyclic carbenes (NHC) in discrete binuclear complexes. The activation energies for the rotation could be tuned by changing the implanted metal. Exchanging Cu to Au resulted in an ∼4.0 kcal/mol reduction in the rotational energy barrier as a result of lower steric demand by elongation of the axle with the noble metal, and a stronger electronic stabilization in the rotational transition state by enhancement of the d-π* interactions between the metal centers and the pyrazine rotator. The Cu(I) rotor complex showed a greater electronic delocalization than the Au(I) rotor complex, causing a red-shifted solid-state emission. Molecular rotation-induced emission quenching was observed in both crystals. The enclosing NHC rotors are easy to prepare, and their rotational motion should be less dependent on packing structures, which are often crucial for many previously documented amphidynamic molecular crystals. The platform from the encapsulating NHC cationic metal complexes and the metal-centered rotation-axis provide a promising scaffold for a novel design of crystalline molecular rotors, including manipulation of rotary dynamics and solid-state emission.
  • Takumi Takeuchi, Ryosuke Shishido, Koji Kubota, Hajime Ito
    Chemical Science 2021年 

    The synthesis of a series of hydrosilylboronates via the selective iridium- or nickel-catalyzed monoborylation of dihydrosilane Si−H bonds is described. The synthesized silylboronates, which bear a single Si−H bond, can...

  • Yadong Pang, Joo Won Lee, Koji Kubota, Hajime Ito
    Angewandte Chemie International Edition 59 50 22570 - 22576 2020年12月07日 [査読有り]
  • Yuichi Kitagawa, Fumiya Suzue, Takayuki Nakanishi, Koji Fushimi, Tomohiro Seki, Hajime Ito, Yasuchika Hasegawa
    Communications Chemistry 3 1 2020年12月01日 [査読有り][通常論文]
     
    © 2020, The Author(s). Photosensitizer design to allow effective use of low-energy light is important for developing photofunctional materials. Herein, we describe a rational photosensitizer design for effective use of low-energy light. The developed photosensitizer is a stacked nanocarbon based on a rigid polyaromatic framework, which allows efficient energy transfer from the low-energy T1 level to the energy acceptor. We prepared an Eu(III) complex consisting of a luminescent center (Eu(III)) and stacked-coronene photosensitizer. The brightness of photosensitized Eu(III) excited using low-energy light (450 nm) is more than five times higher than the maximum brightness of previously reported Eu(III) complexes.
  • Koji Kubota, Rikuro Takahashi, Minami Uesugi, Hajime Ito
    ACS Sustainable Chemistry & Engineering 2020年11月09日 [査読有り]
  • Ryosuke Shishido, Minami Uesugi, Rikuro Takahashi, Tsuyoshi Mita, Tatsuo Ishiyama, Koji Kubota, Hajime Ito
    Journal of the American Chemical Society 142 33 14125 - 14133 2020年08月19日 [査読有り][通常論文]
     
    Copyright © 2020 American Chemical Society. Compared to carbon-based nucleophiles, the number of silicon-based nucleophiles that is currently available remains limited, which significantly hampers the structural diversity of synthetically accessible silicon-based molecules. Given the high synthetic utility and ease of handling of carbon-based boron nucleophiles, silicon-based boron nucleophiles, i.e., silylboranes, have attracted considerable interest in recent years as nucleophilic silylation reagents that are activated by transition-metal catalysts or bases. However, the range of practically accessible silylboranes remains limited. In particular, the preparation of sterically hindered and functionalized silylboranes remains a significant challenge. Here, we report the use of rhodium and platinum catalysts for the direct borylation of hydrosilanes with bis(pinacolato)diboron, which allows the synthesis of new trialkylsilylboranes that bear bulky alkyl groups and functional groups as well as new dialkylarylsilylboranes that are difficult to synthesize via conventional methods using alkali metals. We further demonstrate that these compounds can be used as silicon nucleophiles in organic transformations, which significantly expands the scope of synthetically accessible organosilicon compounds compared to previously reported methods. Thus, the present study can be expected to inspire the development of efficient methods for novel silicon-containing bioactive molecules and organic materials with desirable properties. We also report the first 11B{1H} and 29Si{1H} NMR spectroscopic evidence for the formation of i-Pr3SiLi generated by the reaction of i-Pr3Si-B(pin) with MeLi.
  • Kenichiro Omoto, Toyotaka Nakae, Masaki Nishio, Yoshinori Yamanoi, Hidetaka Kasai, Eiji Nishibori, Takaki Mashimo, Tomohiro Seki, Hajime Ito, Kazuki Nakamura, Norihisa Kobayashi, Naofumi Nakayama, Hitoshi Goto, Hiroshi Nishihara
    Journal of the American Chemical Society 2020年07月22日 [査読有り][通常論文]
  • Tamae Seo, Koji Kubota, Hajime Ito
    Journal of the American Chemical Society 142 22 9884 - 9889 2020年06月03日 [査読有り][通常論文]
     
    Palladium-catalyzed Suzuki-Miyaura cross-coupling reactions of liquid, unbiased dibromoarenes under mechanochemical conditions selectively afford the monoarylated products. The lower reactivity of the crystalline monoarylated products relative to the liquid starting materials should be attributed predominantly to the low diffusion efficiency of the former in the reaction mixture, which results in a selective monoarylation. The present study sheds light on a novel approach using in situ phase transitions in solids to design selective organic transformations that are difficult to achieve via conventional solution-based synthesis.
  • Tomohiro Seki, Chi Feng, Kentaro Kashiyama, Shunichi Sakamoto, Yuichi Takasaki, Toshiyuki Sasaki, Satoshi Takamizawa, Hajime Ito
    Angewandte Chemie 132 23 8924 - 8928 2020年06月02日 [査読有り]
  • Tomohiro Seki, Chi Feng, Kentaro Kashiyama, Shunichi Sakamoto, Yuichi Takasaki, Toshiyuki Sasaki, Satoshi Takamizawa, Hajime Ito
    Angewandte Chemie International Edition 59 23 8839 - 8843 2020年06月02日 [査読有り][通常論文]
     
    Ferroelasticity has been reported for several types of molecular crystals, which show mechanical-stress-induced shape change under twinning and/or spontaneous formation of strain. Aiming to create materials that exhibit both ferroelasticity and light-emission characteristics, we discovered the first examples of ferroelastic luminescent organometallic crystals. Crystals of arylgold(I)(N-heterocyclic carbene)(NHC) complexes bend upon exposure to anisotropic mechanical stress. X-ray diffraction analyses and stress-strain measurements on these ferroelastic crystals confirmed typical ferroelastic behavior, mechanical twinning, and the spontaneous build-up of strain. A comparison with single-crystal structures of related gold-NHC complexes that do not show ferroelasticity shed light on the structural origins of the ferroelastic behavior.
  • Sota Akiyama, Syogo Nomura, Koji Kubota, Hajime Ito
    The Journal of Organic Chemistry 85 6 4172 - 4181 2020年03月20日 [査読有り]
  • Jumpei Taguchi, Satsuki Matsuura, Tomohiro Seki, Hajime Ito
    Chemistry – A European Journal 26 11 2450 - 2455 2020年02月21日 [査読有り][通常論文]
     
    A new class of borate luminophores has been synthesized by a simple two-step reaction using potassium acyltrifluoroborates (KATs) as starting materials. The hydrazones obtained from reactions between KATs and 2-hydrazinopyridines followed by a cyclization resulted in the unprecedented formation of C,N-chelated six-membered bora-heterocycles. Under consideration of the results of DFT and TD-DFT calculations, four luminophores based on such bora-heterocycles are designed and synthesized, which exhibit a tunable fluorescence range from blue to red in the solid state. Moreover, one of the luminophores exhibits mechanofluorochromism from blue to yellow/green. As a result of the aforementioned mechanochromism of one of these luminophores, white-color emission was achieved by simply mixing the four luminophores.
  • Hiroaki Iwamoto, Yuta Hayashi, Yu Ozawa, Hajime Ito
    ACS Catalysis 2471 - 2476 2020年02月21日 [査読有り][通常論文]
  • Tomohiro Seki, Takaki Mashimo, Hajime Ito
    CHEMISTRY LETTERS 49 2 174 - 177 2020年02月 [査読有り][通常論文]
     
    The thermosalient effect of simple hydrocarbon compounds, including tetraphenylethene, is reported. Single-crystal X-ray diffraction and differential calorimetry analyses of these compounds indicate the absence of thermal phase transitions for their crystal jumps. Thermal expansion coefficient analysis indicates that anisotropic dimension changes of the crystalline lattices are important for this phenomenon.
  • Keiichi Hayama, Ryoto Kojima, Koji Kubota, Hajime Ito
    Organic Letters 2020年01月17日 [査読有り][通常論文]
  • Tomohiro Seki, Kentaro Ida, Hiroyasu Sato, Shinji Aono, Shigeyoshi Sakaki, Hajime Ito
    Chemistry – A European Journal 26 3 735 - 744 2020年01月13日 [査読有り][通常論文]
     
    The first examples of porous molecular crystals that are assembled through Au...Au interactions of gold complex 1 are here reported along with their exchange properties with respect to their guest components. Single-crystal X-ray diffraction (XRD) analyses indicate that the crystal structure of 1/CH2Cl2.pentane is based on cyclic hexamers of 1, which are formed through six Au...Au interactions. The packing of these cyclic hexamers affords a porous architecture, in which the one-dimensional channel segment contains CH2Cl2 and pentane as guests. These guests can be exchanged through operationally simple methods under retention of the host framework of 1, which furnished 1/guest complexes with 26 different guests. A single-crystal XRD analysis of 1/eicosane, which contains the long linear alkane eicosane (n-C20H42), successfully provided its accurately modeled structure within the porous material. These host-guest complexes show chromic luminescence with both blue- and redshifted emissions. Moreover, this porous organometallic material can exhibit luminescent mechanochromism through release of guests.
  • Tomohiro Seki, Naoki Toyoshima, Hajime Ito
    Dalton Transactions 49 7 2073 - 2076 2020年 [査読有り][通常論文]
     
    Mixed crystals composed of two distinct gold isocyanide complexes are reported. Characterization of the mixed crystal formation and mixing ratios are performed by single-crystal X-ray diffraction and nuclear magnetic resonance spectroscopy analyses. By changing the mixing ratio, we achieve continuous changes in the emission lifetimes and the emission quantum yields.
  • Rina Takahashi, Koji Kubota, Hajime Ito
    Chemical Communications 2020年 [査読有り][通常論文]
  • Hajime Ito, Koji Kubota, Yadong Pang, Akira Miura, Hajime Ito
    Science 366 6472 1500 - 1504 2019年12月20日 [査読有り][通常論文]
  • Hajime Ito, Mingoo Jin, Sho Yamamoto, Tomohiro Seki, Hajime Ito, Miguel A. Garcia‐Garibay
    Angewandte Chemie 131 50 18171 - 18178 2019年12月09日 [査読有り][通常論文]
  • Hajime Ito, Mingoo Jin, Sho Yamamoto, Tomohiro Seki, Hajime Ito, Miguel A. Garcia-Garibay
    Angewandte Chemie International Edition 58 50 18003 - 18010 2019年12月09日 [査読有り][通常論文]
  • Kubota Koji, Seo Tamae, Koide Katsumasa, Hasegawa Yasuchika, Ito Hajime
    NATURE COMMUNICATIONS 10 1 2019年12月 [査読有り][通常論文]
  • Hajime Ito, Ryosuke Shishido, Ikuo Sasaki, Tomohiro Seki, Tatsuo Ishiyama, Hajime Ito
    Chemistry – A European Journal 25 56 12924 - 12928 2019年10月08日 [査読有り][通常論文]
  • Yasuchika Hasegawa, Takafumi Matsui, Yuichi Kitagawa, Takayuki Nakanishi, Tomohiro Seki, Hajime Ito, Yuta Nakasaka, Takao Masuda, Koji Fushimi
    Chemistry - A European Journal 25 53 12308 - 12315 2019年09月20日 [査読有り][通常論文]
     
    © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Oxygen-sensitive and near-infrared (NIR) luminescent YbIII coordination polymers incorporating ligands based on pyrene derivatives were synthesized: YbIII–TBAPy and YbIII–TIAPy (TBAPy: 1,3,6,8-tetrakis(p-benzoate)pyrene; TIAPy: 1,3,6,8-tetrakis(3,5-isophthalic acid)pyrene). The coordination structures of these materials have been characterized by means of electrospray ionization mass spectrometry, X-ray diffraction analysis, and thermogravimetric analysis. Moreover, the porous structure of YbIII–TIAPy has been evaluated by measuring its N2 adsorption isotherm. The NIR luminescence properties of YbIII–TBAPy and YbIII–TIAPy have been examined by acquiring emission spectra and determining emission lifetimes under air or argon and in vacuo. YbIII–TIAPy exhibited high thermal stability (with a decomposition temperature of 400 °C), intense luminescence (with an emission quantum yield under argon of 6.6 %), and effective oxygen-sensing characteristics. These results suggest that NIR luminescent YbIII coordination polymers prepared using pyrene derivatives could have applications in novel thermo-stable oxygen sensors.
  • Akiyama, S, Kubota, K, Mikus, M. S, Paioti, P. H. S, Romiti, F, Liu, Q, Zhou, Y, Hoveyda, A. H, Ito, H
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 58 35 11998 - 12003 2019年08月26日 [査読有り][通常論文]
  • Iwamoto, H, Endo, K, Ozawa, Y, Watanabe, Y, Kubota, K, Imamoto, T, Ito, H
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 58 32 11112 - 11117 2019年08月05日 [査読有り][通常論文]
  • Hajime Ito, Jumpei Taguchi, Takumi Takeuchi, Rina Takahashi, Fabio Masero, Hajime Ito
    Angewandte Chemie International Edition 58 22 7146 - 7146 2019年05月27日 [査読有り][通常論文]
  • Taguchi Jumpei, Takeuchi Takumi, Takahashi Rina, Masero Fabio, Ito Hajime
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 58 22 7299 - 7303 2019年05月27日 [査読有り][通常論文]
  • Kato Masako, Ito Hajime, Hasegawa Miki, Ishii Kazuyuki
    CHEMISTRY-A EUROPEAN JOURNAL 25 20 5105 - 5112 2019年04月05日 [査読有り][通常論文]
  • Pang Yadong, Ishiyama Tatsuo, Kubota Koji, Ito Hajime
    CHEMISTRY-A EUROPEAN JOURNAL 25 18 4654 - 4659 2019年03月27日 [査読有り][通常論文]
  • Isono Takuya, Kawakami Nao, Watanabe Kodai, Yoshida Kohei, Otsuka Issei, Mamiya Hiroaki, Ito Hajime, Yamamoto Takuya, Tajima Kenji, Borsali Redouane, Satoh Toshifumi
    POLYMER CHEMISTRY 10 9 1119 - 1129 2019年03月07日 [査読有り][通常論文]
  • Yadong Pang, Tatsuo Ishiyama, Koji Kubota, Hajime Ito
    Chemistry – A European Journal 25 18 4532  Wiley 2019年03月 [査読有り][通常論文]
  • Aono Shinji, Seki Tomohiro, Ito Hajime, Sakaki Shigeyoshi
    JOURNAL OF PHYSICAL CHEMISTRY C 123 8 4773 - 4794 2019年02月28日 [査読有り][通常論文]
  • The Direct Dimesitylborylation of Benzofuran Derivatives via an Iridium-Catalyzed C–H Activation with Silyldimesitylborane
    Ryosuke Shishido, Ikuo Sasaki, Tomohiro Seki, Tatsuo Ishiyama, Hajime Ito
    Chem. Eur. J. (IF:5.16) Just Accepted 2019年 [査読有り][通常論文]
  • Seo, T, Ishiyama, T, Kubota, K, Ito, H
    CHEMICAL SCIENCE 10 35 8202 - 8210 2019年 [査読有り][通常論文]
  • Seki Tomohiro, Kashiyama Kentaro, Ito Hajime
    DALTON TRANSACTIONS 48 21 7105 - 7109 2019年 [査読有り][通常論文]
  • Seki Tomohiro, Mashimo Takaki, Ito Hajime
    CHEMICAL SCIENCE 10 15 4185 - 4191 2019年 [査読有り][通常論文]
  • Kubota Koji, Uesugi Minami, Osaki Shun, Ito Hajime
    ORGANIC & BIOMOLECULAR CHEMISTRY 17 23 5680 - 5683 2019年 [査読有り][通常論文]
  • Seki Tomohiro, Kobayashi Koh, Mashimo Takaki, Ito Hajime
    CHEMICAL COMMUNICATIONS 54 93 13160  2018年12月04日 [査読有り][通常論文]
  • Hirai Yuichi, da Rosa Pedro, Paulo Ferreira, Nakanishi Takayuki, Kitagawa Yuichi, Fushimi Koji, Seki Tomohiro, Ito Hajime, Hasegawa Yasuchika
    INORGANIC CHEMISTRY 57 23 14653 - 14659 2018年12月03日 [査読有り][通常論文]
  • Ito Masami, Mera Akane, Mashimo Takaki, Seki Tomohiro, Karanjit Sangita, Ohashi Eisaku, Nakayama Atsushi, Kitamura Kei, Hamura Toshiyuki, Ito Hajime, Namba Kosuke
    CHEMISTRY-A EUROPEAN JOURNAL 24 67 17727 - 17733 2018年12月03日 [査読有り][通常論文]
  • Hiroaki Iwamoto, Tsuneo Imamoto, Hajime Ito
    Nature Communications 9 1 2018年12月 [査読有り][通常論文]
  • Ito Hajime, Seo Tamae, Kojima Ryoto, Kubota Koji
    CHEMISTRY LETTERS 47 10 1330 - 1332 2018年10月 [査読有り][通常論文]
  • Hasegawa Yasuchika, Miura Yui, Kitagawa Yuichi, Wada Satoshi, Nakanishi Takayuki, Fushimi Koji, Seki Tomohiro, Ito Hajime, Iwasa Takeshi, Taketsugu Tetsuya, Gon Masayuki, Tanaka Kazuo, Chujo Yoshiki, Hattori Shingo, Karasawa Masanobu, Ishii Kazuyuki
    CHEMICAL COMMUNICATIONS 54 76 10695 - 10697 2018年09月28日 [査読有り][通常論文]
  • Pang Yadong, Kojima Ryoto, Ito Hajime
    ORGANIC & BIOMOLECULAR CHEMISTRY 16 34 6187 - 6190 2018年09月14日 [査読有り][通常論文]
  • Shun Omagari, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Koji Fushimi, Hajime Ito, Andries Meijerink, Yasuchika Hasegawa
    Journal of Luminescence 201 170 - 175 2018年09月 [査読有り][通常論文]
     
    © 2018 Elsevier B.V. In luminescent lanthanide (Ln(III)) complexes, the yield and the lifetime of triplet excited state of organic ligands are crucial factors that affect the ligands-to-Ln(III) energy transfer efficiency. Such factors are dependent on spin-orbit coupling induced by the Ln(III) ions that mixes different multiplicity states through heavy atom and paramagnetic effects. We investigated the role of these effects on the energy transfer efficiency in synthesized nonanuclear Yb-Gd / Yb-Lu clusters ([Ln9(µ-OH)10(butyl salicylate)16]NO3, Ln9 = YbnGd9-n or YbnLu9-n, n = 0, 1, 3, 7, and 9). Based on the intensity of the fluorescence and phosphorescence of the ligands, the spin-orbit coupling strength was in the order of Yb(III) > Gd(III) > Lu(III). Various photophysical processes affecting the energy transfer efficiency in YbnGd9-n and YbnLu9-n clusters are discussed from the perspective of spin-orbit coupling and give insight in how to optimize energy transfer efficiencies.
  • Ozawa Yu, Iwamoto Hiroaki, Ito Hajime
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 256 2018年08月19日 [査読有り][通常論文]
  • Takahashi Rina, Taguchi Jumpei, Bode Jeffery, Ito Hajime
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 256 2018年08月19日 [査読有り][通常論文]
  • Motoyama Sadako, Ito Hajime, Sarai Masayoshi, Nagahara Yasuomi, Miyajima Keiichi, Matsumoto Ryota, Doi Yujiro, Kataoka Yumi, Takahashi Hiroshi, Ozaki Yukio, Toyama Hiroshi, Katada Kazuhiro
    CIRCULATION JOURNAL 82 7 1844 - 1851 2018年07月 [査読有り][通常論文]
  • Ryoto Kojima, Sota Akiyama, Hajime Ito
    Angewandte Chemie International Edition 57 24 7196 - 7199 Wiley 2018年06月11日 [査読有り][通常論文]
     
    The first catalytic enantioselective γ-boryl substitution of CF3-substituted alkenes is reported. A series of CF3-substituted alkenes was treated with a diboron reagent in the presence of a copper(I)/Josiphos catalyst to afford the corresponding optically active γ,γ-gem-difluoroallylboronates in high enantioselectivity. The thus obtained products could be readily converted into the corresponding difluoromethylene-containing homoallylic alcohols using highly stereospecific allylation reactions.
  • Tomohiro Seki, Kentaro Ida, Hajime Ito
    Materials Chemistry Frontiers 2 6 1195 - 1200 Royal Society of Chemistry ({RSC}) 2018年06月01日 [査読有り][通常論文]
  • Pedro Paulo Ferreira da Rosa, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Hajime Ito, Koji Fushimi, Yasuchika Hasegawa
    European Journal of Inorganic Chemistry 2018 19 2031 - 2037 2018年05月24日 [査読有り][通常論文]
     
    Seven-coordinate TbIII complexes with strong luminescence and thermosensing properties are reported. Mononuclear [Tb(tmh)3(PEB)] [tmh: 2,2,6,6-tetramethyl-3,5-heptanedione, PEB: (diphenylphosphoryl)ethynyl]benzene and dinuclear [Tb2(tmh)6(m-BPEB)] [m-BPEB: 1,3-bis(diphenylphosphoryl)ethynyl]benzene were characterized by single-crystal X-ray analysis. The quantum yields of [Tb(tmh)3(PEB)] and [Tb2(tmh)6(m-BPEB)] were estimated to be 71 and 39 %, respectively. Thermosensing properties are evaluated by temperature-dependent emission lifetime measurements (Arrhenius analysis), which are affected by the presence of ligand-to-ligand charge transfer (LLCT) bands. The LLCT bands are confirmed by DFT calculations.
  • Hajime Ito
    Pure and Applied Chemistry 90 4 703 - 710 2018年03月28日 [査読有り][通常論文]
     
    Chiral N-heterocyclic organoboronates represent promising intermediates for the preparation of various bioactive and pharmaceutical compounds. We recently reported the first asymmetric dearomative borylation of indoles by copper-catalyzed borylation. Then we further developed dearomatization/enantioselective borylation sequence. Chiral 3-boryl-tetrahydropyridines and chiral boryl-tetrahydroquinolines via the copper(I)-catalyzed regio-, diastereo- and enantioselective borylation of 1,2-dihydropyridines and 1,2-dihydroquinilines, which were prepared by the partial reduction of the corresponding pyridine or quinoline derivatives. This dearomatization/enantioselective borylation procedures provide a direct access to chiral piperidines and tetrahydroquinolines from readily available pyridines or quinolines in combination with the stereospecific transformation of the stereogenic C-B bond.
  • Mingoo Jin, Toshiki Sumitani, Hiroyasu Sato, Tomohiro Seki, Hajime Ito
    Journal of the American Chemical Society 140 8 2875 - 2879 2018年02月28日 [査読有り][通常論文]
     
    Luminescence alterations in solid-state materials upon external stimulations have attracted much attention due to their potential for the development of highly functional devices or sensors. We have previously reported the first examples of mechano-induced single-crystal-to-single-crystal (SCSC) phase transitions of gold(I) isocyanide complexes under concomitant emission-color changes. However, the reverse phase transitions of the crystals obtained after mechanical stimulation have not yet been achieved. Herein, a reversible change of the luminescence based on two SCSC phase transitions via mechanical cutting and solvent-vapor adsorption is described. Crystallization of a gold(I) complex that bears CF3 and biaryl moieties from CH2Cl2/MeOH afforded a green-emitting single crystal packed in a polar space group (Pna21). The green-emitting single crystals included MeOH molecules. Upon cutting the crystal under MeOH vapor at 22 °C, the green-emitting single crystal spontaneously changed into a centrosymmetric orange-emitting single crystal (P1Ì) under concomitant release of MeOH. Remarkably, the initial green-emitting crystal could be recovered from the orange-emitting crystal by a solvent-induced SCSC transition under saturated MeOH vapor. The combination of two different types of SCSC phase transitions enables the reversible structural and photoluminescent alternations.
  • Kei Yanagisawa, Yuichi Kitagawa, Takayuki Nakanishi, Tomohiro Seki, Koji Fushimi, Hajime Ito, Yasuchika Hasegawa
    Chemistry - A European Journal 24 8 1956 - 1961 2018年02月06日 [査読有り][通常論文]
     
    Temperature-dependent luminescence of a dinuclear EuIII/TbIII complex with a seven-coordinate structure is demonstrated. The dinuclear complex is composed of two lanthanide ions, six tetramethylheptanedionate ligands, and a bidentate phosphine oxide linker ligand. The dinuclear structure of the complex was characterized by single-crystal XRD. Intrinsic 4f–4f emission quantum yields of the dinuclear EuIII and TbIII complexes were 66 and 61 %, respectively. The luminescence color of the dinuclear EuIII/TbIII complex changed from red to green with increasing temperature. The thermosensing range based on the ratio of luminescence intensity (AEu/ATb) was 100–450 K. The temperature-dependent luminescence is due to the presence of a ligand-to-metal charge-transfer state.
  • Shun Omagari, Takayuki Nakanishi, Yuichi Hirai, Yuichi Kitagawa, Tomohiro Seki, Koji Fushimi, Hajime Ito, Yasuchika Hasegawa
    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 5 561 - 567 2018年02月 [査読有り][通常論文]
     
    Phonons are important in energy transfer for compensating the energy mismatch between a donor and an acceptor. In inorganic hosts doped with lanthanides, phonon-assisted energy transfer can lead to quenching by a direct transfer of the energy to the phonon mode of the acceptor lanthanide. We demonstrate that this also applies to lanthanide coordination polymers and is the reason for the weak concentration quenching in this type of material. [YbxGd1-x(hfa)(3)dpbp](n) [x = 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1; hfa: hexafluoroacetylacetonate, dpbp: 4,4'-bis(diphenylphosphoryl)biphenyl] coordination polymers have been synthesized and their photophysical properties investigated. The single-exponential emission lifetimes of Yb3+ gradually decreased with increasing concentration of Yb3+. Qualitative agreement was achieved between the experimental and theoretical lifetimes by using the phonon-assisted energy-transfer-induced quenching model, which indicates that the origin of the concentration quenching in the coordination polymers is phonon-assisted energy transfer.
  • Tomohiro Seki, Koh Kobayashi, Takaki Mashimo, Hajime Ito
    Chemical Communications 54 79 11136  Royal Society of Chemistry ({RSC}) 2018年 [査読有り][通常論文]
  • Yu Ozawa, Hiroaki Iwamoto, Hajime Ito
    Chemical Communications 54 39 4991 - 4994 2018年 [査読有り][通常論文]
     

    We report the first copper(i)-catalysed intramolecular alkylboration of terminal allenes with an alkyl halide moiety.

  • Masanori Yamamoto, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Hajime Ito, Koji Fushimi, Yasuchika Hasegawa
    Bulletin of the Chemical Society of Japan 91 1 6 - 11 2018年 [査読有り][通常論文]
     
    Lanthanide (Ln3+) complexes composed of luminescent Eu3+ complex and joint metal blocks (Al3+, Zn2+ and Pd2+ complexes) are reported. The Eu3+ complexes [Eu(hfa)3- (dppy)2PdCl2]n (Eu-Pd), [Eu(hfa)3(dppy)2ZnCl2]n (Eu-Zn) and [Eu(hfa)3(dppy)4AlCl3]n (Eu-Al) (hfa: hexafluoroacetylacetonato, dppy: 4-pyridyldiphenylphosphine oxide) were synthesized by the complexation of [Eu(hfa)3(H2O)2] with [MCln-(dppy)m] (M = Pd2+, Zn2+ and Al3+). These predicted structures were estimated using single-crystal X-ray structural analyses and DFT calculations. Photophysical properties of these complexes were evaluated based on the emission lifetimes and emission quantum yields. The emission quantum yields are dependent on the moiety of the joint metal blocks. Eu-Al complex shows the largest emission quantum yield (Φff = 72%). In contrast, the emission quantum yield of Eu-Pd is found to be 1.3%. The structures and photophysical properties of Eu3+ complexes linked with joint metal blocks are demonstrated.
  • Nakayama Naofumi, Obata Shigeaki, Hori Yoshikazu, Goto Hitoshi, Seki Tomohiro, Ito Hajime
    JOURNAL OF COMPUTER CHEMISTRY-JAPAN 17 3 155 - 157 2018年 [査読有り][通常論文]
     
    Force field parameters around Au atom that have been lacking in standard parameter set of the MMFF94s were temporarily determined to reproduce the molecular crystal structure of phenyl(phenylisocyanide) gold(I) complex by classical force field calculations. It was confirmed that two polymorphic forms optimized by CONFLEX software with these parameters are in good agreement with the experimental structures. Application of the parameters to other derivatives also gives good results but the Au.. Au distances in some crystal structures are longer than those of the experimental. Therefore, further optimization of these parameters will be required.
  • Mingoo Jin, Tim S. Chung, Tomohiro Seki, Hajime Ito, Miguel A. Garcia-Garibay
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 139 49 18115 - 18121 2017年12月 [査読有り][通常論文]
     
    Here we present a structural design aimed at the control of phosphorescence emission as the result of changes in molecular rotation in a crystalline material. The proposed strategy includes the use of aurophilic interactions, both as a crystal engineering tool and as a sensitive emission probe, and the use of a dumbbell-shaped architecture intended to create a low packing density region that permits the rotation of a central phenylene. Molecular rotor 1, with a central 1,4-diethynylphenylene rotator linked to two gold(I) triphenylphosphane complexes, was prepared and its structure confirmed by single crystal X-ray diffraction, which revealed chains mediated by dimeric aurophilic interactions. We showed that green-emitting crystals exhibit reversible luminescent color changes between 298 and 193 K, which correlate with changes in rotational motion determined by variable-temperature solid-state H-2 NMR spin echo experiments. Fast two-fold rotation with a frequency of ca. 4.00 MHz (tau = 0.25 mu s) at 298 K becomes essentially static below 193 K as emission steadily changes from green to yellow in this temperature interval. A correlation between phosphorescence lifetimes and rotational frequencies is interpreted in terms of conformational changes arising from rotation of the central phenylene, which causes a change in electronic communication between the gold-linked rotors, as suggested by DFT studies. These results and control experiments with analogue 2, possessing a hindered tetramethylphenylene that is unable to rotate in the crystal, suggest that the molecular rotation can be a useful tool for controlling luminescence in the crystalline state.
  • Keiichi Hayama, Koji Kubota, Hiroaki Iwamoto, Hajime Ito
    CHEMISTRY LETTERS 46 12 1800 - 1802 2017年12月 [査読有り][通常論文]
     
    The first C-B bond-forming dearomative carboborylation of heteroaromatic compounds has been achieved using copper(I) catalysis. This reaction includes the regioselective addition of a borylcopper(I) intermediate to indoles, followed by the diastereoselective methylation of the resulting copper(I) enolate intermediate to afford the corresponding 3-boryl-2-methylindolines bearing a quaternary stereogenic center with excellent regio- and diastereoselectivity.
  • Hajime Ito, Yuta Takenouchi
    Synthesis 49 21 4738 - 4744 Georg Thieme Verlag {KG} 2017年11月 [査読有り][通常論文]
     
    A novel approach for the selective synthesis of -substituted -aminoallylboronates through a copper(I)-catalyzed -boryl-substitution of allyl aminals is developed. The reaction proceeds with high yield (up to 88%) and good E/Z selectivity (up to >95:5). Subsequent aldehyde allylation using allylboronates affords (Z)-anti-1,2-amino alcohol derivatives with high stereoselectivity (up to 91% yield, and up to 17:83 E/Z).
  • Eiji Yamamoto, Satoshi Ukigai, Hajime Ito
    SYNLETT 28 18 2460 - 2464 2017年11月 [査読有り][通常論文]
     
    A new reaction has been developed for the formal nucleophilic silyl substitution of aryl halides with silyllithium or silylpotassium reagents. Dimethylphenylsilyllithium reacted with various aryl halides to form the corresponding arylsilanes in moderate to good yields with concomitant formation of the disilanes under the optimized reaction conditions. Mechanistic studies indicated that this silyl substitution reaction progresses through polar halogenophilic attack of silyl nucleophiles.
  • Jumpei Taguchi, Toshiki Ikeda, Rina Takahashi, Ikuo Sasaki, Yasushi Ogasawara, Tohru Dairi, Naoya Kato, Yasunori Yamamoto, Jeffrey W. Bode, Hajime Ito
    Angewandte Chemie 129 44 14035  Wiley-Blackwell 2017年10月 [査読有り][通常論文]
  • Ryoto Kojima, Koji Kubota, Hajime Ito
    CHEMICAL COMMUNICATIONS 53 77 10688 - 10691 2017年10月 [査読有り][通常論文]
     
    We have developed a novel approach for the stereodivergent hydro-defluorination of gem-difluoroalkenes using copper(I) catalysts to obtain stereodefined monofluoroalkenes. Both (Z)- and (E)-terminal monofluoroalkenes were obtained by the hydrodefluorination of gem-difluoroalkenes in the presence of copper(I) catalysts and diboron or hydrosilane, respectively, with high stereoselectivity. DFT calculations were conducted to elucidate the stereoselectivity.
  • Hiroaki Iwamoto, Yu Ozawa, Koji Kubota, Hajime Ito
    JOURNAL OF ORGANIC CHEMISTRY 82 19 10563 - 10573 2017年10月 [査読有り][通常論文]
     
    The copper(I)-catalyzed regio- and stereoselective intramolecular alkylation of propargyl ethers and amines bearing an alkyl electrophilic moiety has been developed. The reaction showed high functional group tolerance and gave highly functionalized alkenylboronates bearing heterocyclic rings, which are versatile synthetic intermediates in organic chemistry. The borylation products can be transformed into multisubstituted alkenes through stereospecific transformations. Mechanistic studies showed that the chemo- and stereoselectivity of copper(I)-catalyzed borylation depends on the type of leaving group. Density functional theory calculations suggested that the regioselectivity of the borylcupration of the alkyne is controlled by the electronic effect of the oxygen atom of the propargyl ether in combination with the steric congestion between the boryl group and the substituent at the propargylic position.
  • Jumpei Taguchi, Toshiki Ikeda, Rina Takahashi, Ikuo Sasaki, Yasushi Ogasawara, Tohru Dairi, Naoya Kato, Yasunori Yamamoto, Jeffrey W. Bode, Hajime Ito
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 56 44 13847 - 13851 2017年10月 [査読有り][通常論文]
     
    A concise synthesis of acylborons was achieved by ozonolysis of alkenyl MIDA (N-methyliminodiacetic acid) boronates. This reaction exhibits excellent functional-group tolerance and is applicable to various acyl MIDA boronates and potassium acyltrifluroborates (KATs) which could not be synthesized by previous methods. In addition, alpha-amino acylborons, which would be essential for peptide ligations, were prepared for the first time. The acylboron of l-alanine was obtained in high enantiopurity and found to be configurationally stable. Oligopeptide synthesis between the alpha-amino KATs and amino acid in dilute aqueous media was studied.
  • Tomohiro Seki, Kentaro Kashiyama, Shiki Yagai, Hajime Ito
    Chemistry Letters 46 9 1415 - 1418 2017年09月05日 [査読有り][通常論文]
  • Kei Yanagisawa, Yuichi Kitagawa, Takayuki Nakanishi, Tomoko Akama, Masato Kobayashi, Tomohiro Seki, Koji Fushimi, Hajime Ito, Tetsuya Taketsugu, Yasuchika Hasegawa
    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 32 3843 - 3848 2017年09月 [査読有り][通常論文]
     
    Luminescent mononuclear seven-coordinate Eu-III complexes, with monocapped-octahedral (point group: C-3v), monocapped-trigonal-prismatic (C-2v), and pentagonal-bipyramidal (D-5h) coordination structures, are reported. The complexes each consist of a Eu-III ion, three tetramethylheptanedionates, and a phosphine oxide derivative. Controlling steric hindrance by means of introducing methyl groups into the phosphine oxide ligands resulted in the formation of three types of coordination polyhedral structures. The coordination geometrical structures of the Eu-III complexes were evaluated by single-crystal X-ray diffraction analysis and shape-factor calculations. The radiative rate constant of the Eu-III complex with a monocapped-octahedral structure was larger than those with monocapped-trigonal-prismatic and pentagonal-bipyramidal structures. Characteristic photophysical properties of the seven-coordinate Eu-III complexes are discussed with TD-DFT calculations and Arrhenius analysis of the ligand-to-metal charge transfer.
  • Eiji Yamamoto, Ryosuke Shishido, Tomohiro Seki, Hajime Ito
    ORGANOMETALLICS 36 16 3019 - 3022 2017年08月 [査読有り][通常論文]
     
    New, bulky tris(trimethylsilyl)silylboronate pinacol and hexylene glycol esters ((TMS)(3)SiB(pin) and (TMS)(3)SiB(hg)) were prepared in 46 and 61% yields, respectively, by the reaction of tris(trimethylsilyl)silylpotassium with the corresponding boron electrophiles. Notably, these silylboronate esters exhibited high stability to air and silica gel and were applied to the transition-metal-free boryl substitution of aryl halides, providing the desired borylated products in high yields with excellent B:Si ratios (up to 96% yield, B/Si = 99/1). These new silylboronate esters were also applied to a sequential borylation/cross-coupling process with various aryl halides, as well as the base-mediated silaboration of styrene.
  • Eiji Yamamoto, Satoshi Maedab, Tetsuya Taketsugub, Hajime Ito
    SYNLETT 28 11 1258 - 1267 2017年07月 [査読有り][通常論文]
     
    Silylboranes are used as borylation reagents for organohalides in the presence of alkoxy bases without transition-metal catalysts. PhMe2Si-B(pin) reacts with a variety of aryl, alkenyl, and alkyl halides, including sterically hindered examples, to provide the corresponding organoboronates in good yields with high borylation/silylation ratios, showing good functional group compatibility. Halogenophilic attack of a silyl nucleophile on organohalides, and subsequent nucleophilic attack on the boron electrophile are identified to be crucial, based on the results of extensive theoretical and experimental studies. This borylation reaction is further applied to the first direct dimesitylboryl (BMes(2)) substitution of aryl halides using Ph2MeSi-BMes(2) and Na(O-t-Bu), affording aryldimesitylboranes, which are regarded as an important class of compounds for organic materials. 1 Introduction 2 Boryl Substitution of Organohalides with PhMe2Si-B(pin)/Alkoxy Bases 3 Mechanistic Investigations 4 DFT Mechanistic Studies Using an Artificial Force Induced Reaction (AFIR) Method 5 Dimesitylboryl Substitution of Aryl Halides with Ph2MeSi-BMes(2)/Na(O-t-Bu) 6 Conclusion
  • Yuichi Hirai, Takayuki Nakanishi, Yuichi Kitagawa, Koji Fushimi, Tomohiro Seki, Hajime Ito, Yasuchika Hasegawa
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 56 25 7171 - 7175 2017年06月 [査読有り][通常論文]
     
    Luminescence upon the grinding of solid materials (triboluminescence, TL) has long been a puzzling phenomenon in natural science and has also attracted attention because of its broad application in optics. It has been generally considered that the TL spectra exhibit similar profiles as those of photoluminescence (PL), although they occur from distinct stimuli. Herein, we describe for the first time a large spectral difference between these two physical phenomena using lanthanide(III) coordination polymers with efficient TL and PL properties. They are composed of emission centers (Tb-III and Eu-III ions), antenna (hexafluoroacetylacetonate=hfa), and bridging ligands (2,5-bis(diphenylphosphoryl)furan=dpf). The emission color upon grinding (yellow TL) is clearly different from that upon UV irradiation (reddish-orange PL) in Tb-III/Eu-III-mixed coordination polymers [Tb,Eu(hfa)(3)(dpf)](n) (Tb/Eu=1). The results directly indicate the discrete excitation processes of PL and TL.
  • Koji Kubota, Shun Osaki, Mingoo Jin, Hajime Ito
    Angewandte Chemie 129 23 6746  Wiley-Blackwell 2017年06月 [査読有り][通常論文]
  • Tomohiro Seki, Koh Kobayashi, Hajime Ito
    CHEMICAL COMMUNICATIONS 53 50 6700 - 6703 2017年06月 [査読有り][通常論文]
     
    The low-temperature-selective mechanochromism of a thienyl gold(I) isocyanide complex is reported. The as-prepared powder of this complex did not show any luminescent color changes upon grinding at room temperature. When cooled below -50 degrees C, the powder showed a blue emission in the absence of a phase transition. Upon grinding this powder below -50 degrees C, a green emission was observed, which indicates notable mechanochromism that only occurs at low temperature.
  • Mingoo Jin, Tomohiro Seki, Hajime Ito
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 139 22 7452 - 7455 2017年06月 [査読有り][通常論文]
     
    Herein, a novel mechano-responsive luminescent (MRL) material based on crystal-to-crystal phase transitions between crystals of a chiral and those of a centrosymmetric space group, accompanied by a change of emission properties, is described. Initially, a gold complex containing a biphenyl moiety, which exhibits an achiral structure in solution, afforded an orange-emitting. amorphous phase together with a viscous isotropic oil after evaporation of the solvent. Upon pricking, the orange-emitting oil spontaneously crystallized either in a centrosymmetric or in a chiral space group while simultaneously changing the emission properties. Remarkably, grinding the chiral crystals induced a solid-state phase transition to the achiral crystals under concomitant changes of the emission properties.
  • Tomohiro Seki, Noriaki Tokodai, Shun Omagari, Takayuki Nakanishi, Yasuchika Hasegawa, Takeshi Iwasa, Tetsuya Taketsugu, Hajime Ito
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 139 19 6514 - 6517 2017年05月 [査読有り][通常論文]
     
    Upon mechanical stimulation, 9-anthryl gold(I) isocyanide complex 3 exhibited a bathochromic shift of its emission color from the visible to the infrared (IR) region, which is unprecedented in its magnitude. Prior to exposure to the mechanical stimulus, the polymorphs 3 alpha and 3 beta exhibit emission wavelength maxima (lambda(em,max)) at 448 and 710 nm, respectively. Upon grinding, the lambda(em,max) of 3 alpha(ground) and 3 beta(ground) are bathochromically shifted to 900 nm, i.e., Delta lambda(em,max) (3 alpha) = 452 nm or 1.39 eV. Polymorphs 3 alpha and 3 beta thus represent the first examples of mechanochromic luminescent materials with lambda(em,max) in the IR region.
  • Hiroaki Iwamoto, Sota Akiyama, Keiichi Hayama, Hajime Ito
    ORGANIC LETTERS 19 10 2614 - 2617 2017年05月 [査読有り][通常論文]
     
    The stereoselective borylative radical cyclization of alkyl halides containing an alkene moiety was developed using a copper(I)/diboron catalyst system. The optimized reaction conditions allowed us to control the chemoselectivity between the allylic substitution and the borylative radical cyclization. The borylation products were subsequently converted to highly functionalized organic compounds by derivatization of the newly formed C-B bond. This borylative radical cyclization offers a novel methodology for compounds. the stereoselective synthesis of various heterocyclic compounds.
  • Yasuchika Hasegawa, Shiori Tateno, Masanori Yamamoto, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Hajime Ito, Koji Fushimi
    CHEMISTRY-A EUROPEAN JOURNAL 23 11 2666 - 2672 2017年02月 [査読有り][通常論文]
     
    Luminescent Eu-III coordination polymers with rigid triangular spacer ligands are reported. The Eu-III coordination polymer, [Eu-3(hfa)(9)(tppb)(2)](n) (hfa: hexafluoroacetylacetonate, tppb: tris(4-diphenylphosphorylphenyl) benzene), shows high thermo-stability (decomposition temperature= 354 degrees C) and photoluminescence quantum yield (Phi(4f-4f)= 82%, photosensitized energy transfer efficiency= 78%). The tribolumines-cence efficiency of Eu-III coordination polymer with triangular spacers under laser pulse irradiation (Nd:YAG, lambda= 1064 nm, pulse width= 5 ns, pulse energy= 0.1 mJ) is calculated to be 49%. Characteristic triangular structure, high emission quantum yield, effective photosensitized energy transfer, and remarkable triboluminescence properties of Eu-III coordination polymers are demonstrated for the first time.
  • K. Kubota, Iwamoto, H. Ito
    ORGANIC & BIOMOLECULAR CHEMISTRY 15 2 285 - 300 2017年01月 [査読有り][通常論文]
     
    This review describes recent advances in direct borylation reactions of organic halides, including both transition-metal-catalyzed and metal-free methods. Since the pioneering work on palladium-catalyzed boryl substitution of aryl halides with a diboron compound reported by Miyaura and co-workers in 1995, various catalytic systems for the borylation of aryl, alkneyl, and alkyl halides have been developed to give a wide range of organoboronate esters that cannot be synthesized using conventional methods. Borylative cyclization of alkyl halides is also discussed.
  • Takenouchi, Yuta, Kojima, Ryoto, Momma, Riko, Ito, Hajime
    Synlett 28 2 270 - 274 2017年01月 [査読有り][通常論文]
     
    A novel approach has been developed for the enantioselective synthesis of -chiral -acetoxyallylboronates via the copper(I)-catalyzed -boryl substitution of allyl acylals. This reaction proceeded with high E/Z selectivity and enantioselectivity (E/Z = >99:1, up to 80% yield, up to 99% ee). The subsequent allylation of aldehyde with the allylboronate afforded the monoprotected anti-1,2-diol derivative with high stereoselectivity.
  • Koji Kubota, Shun Osaki, Mingoo Jin, Hajime Ito
    Angewandte Chemie International Edition 56 23 6646 - 6650 Wiley-Blackwell 2017年 [査読有り][通常論文]
     
    A new method was developed for the first catalytic enantioselective borylation of aliphatic ketones. A variety of substrates reacted efficiently with bis(pinacolato)diboron in the presence of a copper(I)/chiral N-heterocyclic carbene complex catalyst to furnish optically active tertiary α-hydroxyboronates with moderate to high enantioselectivities (up to 94 % ee). Notably, the product could be converted into the chiral tertiary alcohol derivative using a stereospecific boron functionalization process. The theoretical study of the mechanism for the enantioselectivity is also described.
  • Ana B. Cuenca, Ryosuke Shishido, Hajime Ito, Elena Fernandez
    CHEMICAL SOCIETY REVIEWS 46 2 415 - 430 2017年01月 [査読有り][通常論文]
     
    This review is a guided tour along the activation modes and reactivity of B-B, B-Si, B-N, B-S, B-Se and BP reagents, in the absence of any transition metal complex. Here are disclosed the general concepts related to the homolytic and heterolytic cleavage of B-B and B interelement bonds, as well as the generation of new C-B and C interelement bonds, in a selective way. The greener consequences of these novel routes facilitate the gram scale preparations of target functionalised organic compounds. Intrinsic data about the suggested mechanisms and spectroscopic evidence that supports the innovative theories are provided along the review. Since this is a stimulating area of work that has emerged within the last decade, this overview serves as the basis to understand the new trends and hopefully to generate inspiration for future discoveries in the field.
  • Eiji Yamamoto, Kiyotaka Izumi, Ryosuke Shishido, Tomohiro Seki, Noriaki Tokodai, Hajime Ito
    CHEMISTRY-A EUROPEAN JOURNAL 22 49 17547 - 17551 2016年12月 [査読有り][通常論文]
     
    The first dimesitylboryl substitution of aryl halides with a silylborane bearing a dimesitylboryl group in the presence of alkali-metal alkoxides is described. The reactions of aryl bromides or iodides with Ph2MeSi-BMes(2) and Na(OtBu) afforded the desired aryl dimesitylboranes in good to high yields and with high borylation/silylation ratios. Selective reaction of the sterically less-hindered C-Br bond of dibromoarenes provided monoborylated products. This reaction was used to rapidly construct a D-pi-A aryl dimesityl borane with a non-symmetrical biphenyl spacer.
  • Tomohiro Seki, Mingoo Jin, Hajime Ito
    INORGANIC CHEMISTRY 55 23 12309 - 12320 2016年12月 [査読有り][通常論文]
     
    Luminescent compounds that are sensitive to volatile organic solvents are useful for detection of harmful gases. Although such compounds have been reported, discrimination of various types of volatile organic compounds using one compound remains challenging. We reported a series of gold isocyanide complexes that form various crystalline structures with distinct emission properties, which can be interconverted by mechanical stimulation and solvent addition. Here, we report that introduction of a biphenyl unit into a gold isocyanide scaffold (denoted complex 3) enables discrimination of various volatile organic compounds by forming 11 solvent containing crystal structures 3/solvent [solvent can be CHCl3, pyridine (Py), CH2Cl2, CH2Br2, dimethylacetamide (DMA), acetaldehyde (AcH), CH3CN, DMF, (S)-propylene oxide (SPO), rac-propylene oxide (racPO), or acetone] with different emission properties (emission maxima of 490-580 nm). Mechanical stimulation of 3/solvent affords amorphous 3(ground) without solvent inclusion. The resulting 3ground can again detect volatile compounds by forming 3/solvent with concomitant emission color changes. We also afforded a dozen single crystals of 3, which include 11 solvated 3/solvent and one solvent-free 3/none. The molecular arrangements of 3 in 3/solvent and 3/none are all different. Comparison of various crystallographic parameters of 3/solvent and 3/none with their corresponding optical properties indicates that a combination of various structural properties of 3 affects the optical properties of 3. This study reveals that the introduction of a biphenyl moiety could be a useful design to develop versatile indicators for solvents through the formation of multiple luminescent crystal structure.
  • Shun Omagari, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Koji Fushimi, Hajime Ito, Andries Meijerink, Yasuchika Hasegawa
    SCIENTIFIC REPORTS 6 37008  2016年11月 [査読有り][通常論文]
     
    Lanthanide (Ln(III)) complexes form an important class of highly efficient luminescent materials showing characteristic line emission after efficient light absorption by the surrounding ligands. The efficiency is however lowered by back energy transfer from Ln(III) ion to the ligands, especially at higher temperatures. Here we report a new strategy to reduce back energy transfer losses. Nonanuclear lanthanide clusters containing terbium and gadolinium ions, TbnGd9-n clusters ([TbnGd9-n(mu-OH)(10)(but ylsalicylate)(16)](+) NO3-, n = 0, 1, 2, 5, 8, 9), were synthesized to investigate the effect of energy transfer between Tb(III) ions on back energy transfer. The photophysical properties of TbnGd9-n clusters were studied by steady-state and time-resolved spectroscopic techniques and revealed a longer emission lifetime with increasing number of Tb(III) ions in TbnGd9-n clusters. A kinetic analysis of temperature dependence of the emission lifetime show that the energy transfer between Tb(III) ions competes with back energy transfer. The experimental results are in agreement with a theoretical rate equation model that confirms the role of energy transfer between Tb(III) ions in reducing back energy transfer losses. The results provide a new strategy in molecular design for improving the luminescence efficiency in lanthanide complexes which is important for potential applications as luminescent materials.
  • Yuichi Hirai, Takayuki Nakanishi, Yuichi Kitagawa, Koji Fushimi, Tomohiro Seki, Hajime Ito, Yasuchika Hasegawa
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 55 39 12059 - 12062 2016年09月 [査読有り][通常論文]
     
    Novel Eu-III coordination polymers [Eu(hfa)(3)(dpt)](n)(dpt: 2,5-bis(diphenylphosphoryl)thiophene) and [Eu(hfa)(3)(dpedot)](n) (dpedot: 2,5-bis(diphenylphosphoryl)ethylenedioxythiophene) with hydrogen-bonded zipper structures are reported. The coordination polymers are composed of Eu-III ions, hexafluoroacetylacetonato ligands, and thiophene-based phosphine oxide bridges. The zig-zag orientation of single polymer chains induced the formation of densely packed coordination structures with multiple intermolecular interactions, resulting in thermal stability above 300 degrees C. They exhibit a high intrinsic emission quantum yield (ca. 80%) due to their asymmetrical and low-vibrational coordination structures around Eu-III ions. Furthermore, the characteristic alternative orientation of substituents also contributes to the dramatically high ligand-to-metal energy transfer efficiencies of up to 80% in the solid state.
  • Koji Kubota, Yuta Watanabe, Hajime Ito
    ADVANCED SYNTHESIS & CATALYSIS 358 15 2379 - 2384 2016年07月 [査読有り][通常論文]
     
    A novel approach has been developed for the synthesis of chiral 3-boryl-tetrahydroquinolines via the copper(I)-catalyzed regio- and enantioselective protoborylation of 1,2-dihydroquinolines, which were prepared by the partial reduction of the corresponding quinoline derivatives. This dearomatization/enantioselective borylation sequence has been used to provide a facile access to a wide variety of functionalized tetrahydroquinolines under mild conditions from readily available quinoline starting materials in combination with the stereospecific transformation of a stereogenic C-B bond. A theoretical study of the mechanism for the enantioselectivity of the reaction is also described.
  • Ikuo Sasaki, Toshiki Ikeda, Tatsunosuke Amou, Jumpei Taguchi, Hajime Ito, Tatsuo Ishiyama
    Synlett (IF:2.418) 27 10 1582 - 1586 2016年06月 [査読有り][通常論文]
     
    An iridium-catalyzed regioselective C-H borylation of pentafluoroaniline-derived heteroaromatic aldimines has been developed. Various heteroaromatic aldimines underwent borylation by bis(pinacolato)diboron to afford the corresponding borylated products in good yields in the presence of an iridium complex formed in situ from bis(cyclooctadienyl)(methoxy)iridium {[Ir(OMe)(cod)](2)} and 1,10-phenanthroline.
  • Koji Kubota, Mingoo Jin, Hajime Ito
    ORGANOMETALLICS 35 10 1376 - 1383 2016年05月 [査読有り][通常論文]
     
    Density functional theory calculations were performed to validate the proposed reaction mechanism for the enantioselective nudeophilic borylation of a polarized C=O double bond in the presence of diphosphine/borylcopper(I) complexes. Consequently, we successfully elucidated the origin for the regioselectivity and the mechanism for the enantioselectivity of the reaction. We also obtained theoretical explanations for the fact that the presence of a proton source gave a higher reactivity and a better enantioselectivity in the borylation reaction of aldehydes with a copper(I)/(R)-DTBM-SEGPHOS complex catalyst. This study is particularly valuable toward the development and design of novel enantioselective borylation reactions with polarized carbon-heteroatom double bonds.
  • Sasaki I, Taguchi J, Doi H, Ito H, Ishiyama T
    Chemistry, an Asian journal 11 9 1400 - 1405 2016年05月 [査読有り][通常論文]
     
    A new process has been developed for the iridium(I)-catalyzed vinylic C-H borylation of alpha,beta-unsaturated esters with bis(pinacolato) diboron (B(2)pin(2)). These reactions proceeded in octane at temperatures in the range of 80-120 degrees C to afford the corresponding alkenylboronic compounds in high yields with excellent regio- and stereoselectivities. The presence of an aryl ester led to significant improvements in the yields of the acyclic alkenylboronates. Crossover experiments involving deuterated substrates as well as a mixture of stereoisomers confirmed that this reaction proceeds via a 1,4-addition/beta-hydride elimination mechanism. Notably, this reaction was also used to develop a one-pot borylation/Suzuki-Miyaura cross-coupling procedure.
  • Tomohiro Seki, Yuki Takamatsu, Hajime Ito
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 138 19 6252 - 6260 2016年05月 [査読有り][通常論文]
     
    Mechanoinduced phase transitions of emissive organic crystalline materials have received much attention. Although a variety of such luminescent mechanochromic compounds have been reported, it is challenging to develop mechanochromic compounds with crystal-to-crystal phase transitions in which precise structural information about molecular arrangements can be obtained. Here, we report a screening approach to explore mechanochromic compounds exhibiting a crystal-to-crystal phase transition. We prepared 48 para-substituted (R-1) phenyl[para-substituted (R-2) phenyl isocyanide]gold(I) complexes designated R-1-R-2 (six R-1 and eight R-2 substituents) and then performed three-step screening experiments. The first screening step was selection of emissive complexes under UV light, which gave 37 emissive R-1-R-2 complexes. The second screening step involved evaluation of the mechanochromic properties by emission spectroscopy. Twenty-eight complexes were found to be mechanochromic.. The third screening step involved. preparation of single crystals, reprecipitated powders, and ground powders of the 28 mechanochromic R-1-R-2 complexes. The changes in the powder diffraction patterns of these complexes induced by mechanical stimulation were investigated. Two compounds exhibited a crystal-to-crystal phase transition upon mechanical stimulation, including the previously reported H-H complex. Single crystals of the as-prepared and ground forms of the newly discovered CF3-CN complex were obtained. Density functional theory calculations indicated that the mechanoinduced red-shifted emission of CF3-CN is caused by formation of aurophilic interactions. Comparison of the crystal structures of CF3-CN with those of the other complexes suggests that the weaker intermolecular interactions in the as-prepared form are an important structural factor for the observed mechanoinduced crystal-to-crystal phase transition.
  • Koji Kubota, Yuta Watanabe, Keiichi Hayama, Hajime Ito
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 138 13 4338 - 4341 2016年04月 [査読有り][通常論文]
     
    We have developed a novel approach for the synthesis of enantio enriched 3-boryl-tetrahydropyridines via the Cu(I)-catalyzed regio-, diastereo-, and enantioselective protoborylation of 1,2-dihydropyridines, which were obtained by the partial reduction of the pyridine derivatives. This dearomatization/enantioselective borylation stepwise strategy provides facile access to chiral piperidines together with the stereospecific transformation of a stereogenic C-B bond from readily available starting materials. Furthermore, the utility of this method is demonstrated for the concise synthesis of the antidepressant drug (-)-paroxetine. A theoretical study of the reaction mechanism is also described.
  • Ayako Nakajima, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Hajime Ito, Koji Fushimi, Yasuchika Hasegawa
    SCIENTIFIC REPORTS 6 24458  2016年04月 [査読有り][通常論文]
     
    Novel organo-Eu-III luminophores, Eu(hfa)(x)(CPO)(y) and Eu(hfa)(x)(TCPO)(y) (hfa: hexafluoroacetylacetonate, CPO: 4-carboxyphenyl diphenyl phosphine oxide, TCPO: 4,4',4 ''- tricarboxyphenyl phosphine oxide), were synthesized by the complexation of Eu-III ions with hfa moieties and CPO or TCPO ligands. The thermal and luminescent stabilities of the luminophores are extremely high. The decomposition temperature of Eu(hfa)(x)(CPO)(y) and Eu(hfa)(x)(TCPO)(y) were determined as 200 and 450 degrees C, respectively. The luminescence of Eu(hfa)(x)(TCPO)(y) under UV light irradiation was observed even at a high temperature, 400 degrees C. The luminescent properties of Eu(hfa)(x)(CPO)(y) and Eu(hfa)(x)(TCPO)(y) were estimated from emission spectra, quantum yields and lifetime measurements. The energy transfer efficiency from hfa moieties to EuIII ions in Eu(hfa)(x)(TCPO)(y) was 59%. The photosensitized luminescence of hyper-stable Eu(hfa)(x)(TCPO)(y) at 400 degrees C is demonstrated for future photonic applications.
  • Tomohiro Seki, Hajime Ito
    CHEMISTRY-A EUROPEAN JOURNAL 22 13 4322 - 4329 2016年03月 [査読有り][通常論文]
     
    Structural changes to molecular crystals upon mechanical stimulation have attracted attention for sensing, recording, and microactuation. Comprehensive structure information is required to understand relationships between the mechanical force applied, the crystal structure, and the bulk property changes in order to develop general design concepts for mechanoresponsive compounds. Unfortunately, mechanical stimulation of organic crystals typically deteriorates their integrity, preventing detailed structure analyses by single-crystal X-ray diffraction (XRD) methods. However, in the past three years, several interesting studies have been reported in which molecular crystals retain their integrity even after a mechanically induced crystalline structure change. These materials have allowed us to investigate how macroscopic mechanical forces affect the microscopic structures of molecular crystals by single-crystal XRD analyses. This Minireview summarizes current knowledge of mechanically induced structure changes in molecular crystals, which will facilitate research in this field.
  • Tomohiro Seki, Kenta Sakurada, Mai Muromoto, Shu Seki, Hajime Ito
    CHEMISTRY-A EUROPEAN JOURNAL 22 6 1968 - 1978 2016年02月 [査読有り][通常論文]
     
    Mechano-induced phase transitions in organic crystalline materials, which can alter their properties, have received much attention. However, most mechano-responsive molecular crystals exhibit crystal-to-amorphous phase transitions, and the intermolecular interaction patterns in the daughter phase are difficult to characterize. We have investigated phenyl(phenylisocyanide)gold(I) (1) and phenyl(3,5-dimethylphenylisocyanide)gold(I) (2) complexes, which exhibit a mechano-triggered single-crystal-to-single-crystal phase transition. Previous reports of complexes 1 and 2 have focused on the relationships between the crystalline structures and photoluminescence properties; in this work we have focused on other aspects. The face index measurements of complexes 1 and 2 before and after the mechano-induced phase transitions have indicated that they undergo non-epitaxial phase transitions without a rigorous orientational relationship between the mother and daughter phases. Differential scanning calorimetry analyses revealed the phase transition of complex 1 to be enthalpically driven by the formation of new aurophilic interactions. In contrast, the phase transition of complex 2 was found to be entropically driven, with the closure of an empty void in the mother phase. Scanning electron microscopy observation showed that the degree of the charging effect of both complexes 1 and 2 was changed by the phase transitions, which suggests that the formation of the aurophilic interactions affords more effective conductive pathways. Moreover, flash-photolysis time-resolved microwave conductivity measurements revealed that complex 1 increased in conductivity after the phase change, whereas the conductivity of complex 2 decreased. These contrasting results were explained by the different patterns in the aurophilic interactions. Finally, an intriguing disappearing polymorphism of complex 2 has been reported, in which a polymorph form could not be obtained again after some period of time, even with repeated trials. The present studies provide us with a variety of hitherto unknown insights into mechano-responsive molecular crystals, which help us to understand the phase transition behaviors upon mechanical stimulation and establish rational design principles.
  • K. Sakurada, T. Seki, H. Ito
    CrystEngComm 18 38 7217 - 7220 2016年 [査読有り][通常論文]
  • Shiki Yagai, Tomohiro Seki, Hiroaki Aonuma, Kohsuke Kawaguchi, Takashi Karatsu, Takuma Okura, Aya Sakon, Hidehiro Uekusa, Hajime Ito
    CHEMISTRY OF MATERIALS 28 1 234 - 241 2016年01月 [査読有り][通常論文]
     
    Photoluminescent materials that exhibit tunable emission properties when subjected to mechanical stimuli have numerous potential applications. Although many organic/inorganic and organometallic compounds display this property, called mechanochromic luminescence, most of these materials undergo a crystalline-to-amorphous (C -> A) phase transition; examples of crystalline-to-crystalline (C-1 -> C-2) transformation are rare. Single-crystal X-ray diffraction may allow direct analysis of the molecular packing of mechanochromic luminescence materials before and after C-1 -> C-2 transformation, which may help to understand the underlying mechanism of this transformation. Reported herein is a mechanochromic luminescence material that displays an unprecedented type of C-1 -> C-2 transformation mediated by a transient amorphous phase (C-1 -> [A] -> C-2). This mechanochromic luminescence material was developed by introducing soft triethylene glycol side chains in a crystalline gold(I) complex that exhibits mechanochromic luminescence based on a C A phase transition. When this new gold(I) complex bearing triethylene glycol chains was subjected to a mechanical or thermal stimulus, dynamic phase changes were observed with irreversible luminescence color changes from blue to yellow to green in both the cases. The crystallinity of the mechanically generated C-2 phase was lower than that of the thermally generated C-2 phase. This is because the mechanically induced C-1 -> [A] -> C-2 process was finished within seconds, whereas the thermal C-1 -> [A] -> C-2 process occurred over a few minutes. To control the C-1 -> [A] -> C-2 transformation, we doped the complex with an inactive soft component. This successfully made the transformation reversible (from green to blue) upon thermal annealing of the mechanically obtained C-2 phase. This approach allowed the development of an imaging process involving invisible information storage even under UV illumination.
  • Eiji Yamamoto, Ryoto Kojima, Koji Kubota, Hajime Ito
    SYNLETT 27 2 272 - 276 2016年01月 [査読有り][通常論文]
     
    Copper(I)-catalyzed diastereoselective borylative exo-cyclization of alkenyl ketones with bis(pinacolato)diboron is reported. The reaction of alkenyl aryl ketones under a CuCl/Xantphos catalyst system provides four- or five-membered-ring syn-2-(borylmethyl)cycloalkanol derivatives in good yields with high syn selectivities. The utility of this method is demonstrated by further transformations of the cyclic products.
  • Hiroaki Iwamoto, Koji Kubota, Hajime Ito
    CHEMICAL COMMUNICATIONS 52 35 5916 - 5919 2016年 [査読有り][通常論文]
     
    A new method has been developed for the Markovnikov hydroboration of alkyl-substituted terminal alkenes. Notably, the use of a bulky bisphosphine-copper(I) catalyst system resulted in high regioselectivity to afford secondary alkylboronates from the corresponding terminal alkenes (branch/linear = 92 : 8-97: 3). This method also exhibited good functional group compatibility.
  • Mingoo Jin, Tomohiro Seki, Hajime Ito
    CHEMICAL COMMUNICATIONS 52 52 8083 - 8086 2016年 [査読有り][通常論文]
     
    Luminescent mechanochromism of a chiral gold(I) complex is investigated. The racemic and homochiral forms of the gold(I) complex possess distinct crystal packing arrangements with different emission colors. Upon mechanical stimulation, both crystals transform into amorphous powders that exhibit similar emission colors.
  • Kei Yanagisawa, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Tomoko Akama, Masato Kobayashi, Tetsuya Taketsugu, Hajime Ito, Koji Fushimi, Yasuchika Hasegawa
    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 28 4769 - 4774 2015年10月 [査読有り][通常論文]
     
    Enhanced luminescence properties of mononuclear lanthanide complexes with asymmetric seven-coordination structures are reported for the first time. The lanthanide complexes are composed of a lanthanide ion (Eu-III or Tb-III), three tetramethyl heptanedionato ligands, and one triphenylphosphine oxide ligand. The coordination geometries of the lanthanide complexes have been evaluated by using single-crystal X-ray analyses and shape-measurement calculations. The complexes are categorized to be seven-coordinate monocapped octahedral structures (point group C-3v). The seven-coordinate lanthanide complexes show high intrinsic emission quantum yields, extra-large radiative rate constants, and unexpected small nonradiative rate constants. The brilliant luminescence properties have been elucidated in terms of the asymmetric coordination geometry and small vibrational quanta related to thermal relaxation.
  • Koji Kubota, Keiichi Hayama, Hiroaki Iwamoto, Hajime Ito
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 54 30 8809 - 8813 2015年07月 [査読有り][通常論文]
     
    The enantioselective borylative dearomatization of a heteroaromatic compound has been achieved using a copper(I) catalyst and a diboron reagent. This reaction involves the regio- and enantioselective addition of active borylcopper(I) species to indole-2-carboxylates, followed by the diastereoselective protonation of the resulting copper(I) enolate to give the corresponding chiral indolines, which bear consecutive stereogenic centers.
  • Ikuo Sasaki, Jumpei Taguchi, Shotaro Hiraki, Hajime Ito, Tatsuo Ishiyama
    CHEMISTRY-A EUROPEAN JOURNAL 21 25 9236 - 9241 2015年06月 [査読有り][通常論文]
     
    The regiodivergent CH borylation of 2,5-disubstituted heteroarenes with bis(pinacolato)diboron was achieved by using iridium catalysts formed in situ from [Ir(OMe)(cod)](2)/dtbpy (cod=1,5-cyclooctadiene, dtbpy: 4,4-di-tert-butyl-2,2-bipyridine) or [Ir(OMe)(cod)](2)/2AsPh(3). When [Ir(OMe)(cod)](2)/dtbpy was used as the catalyst, borylation at the 4-position proceeded selectively to afford 4-borylated products in high yields (dtbpy systemA). The regioselectivity changed when the [Ir(OMe)(cod)](2)/2AsPh(3) catalyst was used; 3-borylated products were obtained in high yields with high regioselectivity (AsPh3 systemB). The regioselectivity of borylation was easily controlled by changing the ligands. This reaction was used in the syntheses of two different bioactive compound analogues by using the same starting material.
  • Sadako Motoyama, Hajime Ito, Yukio Ozaki
    CIRCULATION JOURNAL 79 5 969 - 971 2015年05月 [査読有り][通常論文]
  • Yuichi Hirai, Takayuki Nakanishi, Yuichi Kitagawa, Koji Fushimi, Tomohiro Seki, Hajime Ito, Hiroyuki Fueno, Kazuyoshi Tanaka, Toshifumi Satoh, Yasuchika Hasegawa
    INORGANIC CHEMISTRY 54 9 4364 - 4370 2015年05月 [査読有り][通常論文]
     
    Syntheses of novel luminescent Eu(III) coordination glasses 1 ([Eu(hfa)(3)(o-dpeb)](2)), 2 ([Eu(hfa)(3)(m-dpeb)](3)), and 3 ([Eu(hfa)(3)(p-dpeb)](n)) are reported. They are composed of Eu(III) ions, hexafluoroacetylacetonato (hfa) ligands, and unique bent-angled phosphine oxide (o-, m-, p-dpeb) ligands with ethynyl groups. Their coordination structures and glass formability are dependent on the regiochemistry of substitution in regard to the internal benzene core. Single-crystal X-ray analyses and DFT calculation reveals dinuclear, trinuclear, and polymer structures for Eu(III) coordination glasses 1, 2, and 3, respectively. Those compounds show characteristic glass-transition (T-g = 25-96 degrees C) and strong luminescence properties (phi(Ln) = 72-94%).
  • Yasuchika Hasegawa, Nao Sato, Yuichi Hirai, Takayuki Nakanishi, Yuichi Kitagawa, Atsushi Kobayashi, Masako Kato, Tomohiro Seki, Hajime Ito, Koji Fushimi
    JOURNAL OF PHYSICAL CHEMISTRY A 119 20 4825 - 4833 2015年05月 [査読有り][通常論文]
     
    Enhanced luminescence of a lanthanide complex with dynamic polarization of the excited state and molecular motion is introduced. The luminescent lanthanide complex is composed of one Eu(hfa)(3) (hfa, hexafluoroacetylacetonate) and two phosphine oxide ligands with ruthenocenyl units Rc, [Eu(hfa)(3)(RcPO)(2)] (RcPO = diphenylphosphorylruthenocene). The ruthenocenyl units in the phosphine oxide ligands play an important role of switching for dynamic molecular polarization and motion in liquid media. The oxidation states of the ruthenocenyl unit (Rc(1+)/Rc(1+)) are controlled by potentiostatic polarization. Eu(III) complexes attached with bidentate phosphine oxide ligands containing ruthenocenyl units, [Eu(hfa)(3)(RcBPO)] (RcBPO = 1,1'-bis(diphenylphosphoryl)ruthenocene), and with bidentate phosphine oxide ligands, [Eu(hfa)(3)(BIPHEPO)] (BIPHEPO =1,1'-biphenyl-2,2'-diylbis(diphenylphosphine oxide), were also prepared as references. The coordination structures and electrochemical properties were analyzed using single crystal X-ray analysis, cyclic voltammetry, and absorption spectroscopy measurements. The luminescence properties were estimated using an optoelectrochemical cell. Under potentiostatic polarization, a significant enhancement of luminescence was successfully observed for [Eu(hfa)(3)(RcPO)(2)], while no spectral change was observed for [Eu(hfa)(3)(RcBPO)]. In this study, the remarkable enhanced luminescence phenomena of Eu(III) complex based on the dynamic molecular motion under potentiostatic polarization have been performed.
  • Ryohei Uematsu, Eiji Yamamoto, Satoshi Maeda, Hajime Ito, Tetsuya Taketsugu
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 137 12 4090 - 4099 2015年04月 [査読有り][通常論文]
     
    Theoretical and experimental studies have been conducted to elucidate the mechanism of the formal nucleophilic boryl substitution of aryl and alkyl bromides with silylborane in the presence of potassium methoxide. Density functional theory was used in conjunction with the artificial force induced reaction method in the current study to determine the mechanism of this reaction. The results of this analysis led to the identification of a unique carbanion-mediated mechanism involving the halogenophilic attack of a silyl nucleophile on the bromine atom of the substrate. These calculations have, therefore, provided a mechanistic rationale for this counterintuitive borylation reaction. Furthermore, the good functional group compatibility and high reactivity exhibited by this reaction toward sterically hindered substrates can be understood in terms of the low activation energy required for the reaction of the silyl nucleophile with the bromine atom of the substrate and the subsequent rapid and selective consumption of the carbanion species by the in situ generated boron electrophile. The results of an experimental study involving the capture of the anion intermediate provided further evidence in support of the generation of a carbanion species during the course of this reaction. The anomalous formal nucleophilic borylation mechanism reported in this study could be used to provide new insights into silicon and boron chemistry.
  • Shun Omagari, Takayuki Nakanishi, Tomohiro Seki, Yuichi Kitagawa, Yumie Takahata, Koji Fushimi, Hajime Ito, Yasuchika Hasegawa
    JOURNAL OF PHYSICAL CHEMISTRY A 119 10 1943 - 1947 2015年03月 [査読有り][通常論文]
     
    The photophysical properties of the novel nonanuclear Tb(III) clusters Tb-L1 and Tb-L2 involving the ligands methyl 4-methylsalicylate (L1) and methyl 5-methylsalicylate (L2) are reported. The position of the methyl group has an effect on their photophysical properties. The prepared nonanuclear Tb(III) clusters were identified by fast atom bombardment mass spectrometry and powder X-ray diffraction. Characteristic photophysical properties, including photoluminescence spectra, emission lifetimes, and emission quantum yields, were determined. The emission quantum yield of Tb-L1 (Phi(pi pi)* = 31%) was found to be 13 times larger than that of Tb-L2 (Phi(pi pi)* = 2.4%). The photophysical characterization and DFT calculations reveal the effect of the methyl group on the electronic structure of methylsalicylate ligand. In this study, the photophysical properties of the nonanuclear Tb(III) clusters are discussed in relation to the methyl group on the aromatic ring of the methylsalicylate ligand.
  • Koji Kubota, Hiroaki Iwamoto, Eiji Yamamoto, Hajime Ito
    ORGANIC LETTERS 17 3 620 - 623 2015年02月 [査読有り][通常論文]
     
    Stereoselective silicon-tethered alkylboration of alkynes in the presence of a copper(I) catalyst and a diboron reagent provided the corresponding cyclic alkenylboronates in high yields (up to 99% yield) with excellent regio- and syn-selectivities (E/Z = <1:99). The products, which can be considered as the formal alkyne intermolecular alkylboration products, undergo subsequent selective derivatization, including ring opening, to give functionalized trans-stilbene derivatives.
  • Hiroaki Iwamoto, Koji Kubota, Eiji Yamamoto, Hajime Ito
    CHEMICAL COMMUNICATIONS 51 47 9655 - 9658 2015年 [査読有り][通常論文]
     
    The selective boryl substitution of alkyl halides bearing terminal C=C double bonds has been achieved using a copper(I)/tricyclohexylphosphine or copper(I)/o-diphenylphosphinophenol catalyst. This reaction represents a useful complementary approach to conventional procedures for the hydroboration of C=C double bonds or the borylative cyclization of alkyl halides bearing terminal alkenes.
  • Tomohiro Seki, Kenta Sakurada, Hajime Ito
    CHEMICAL COMMUNICATIONS 51 73 13933 - 13936 2015年 [査読有り][通常論文]
     
    The mechanochromic compound 1 forms green-emitting crystals (1g) and blue-emitting crystals (1b) that exhibit two intriguing responses to mechanical stimulation. Upon mechanical stimulation, the emission color of 1g does not change but its crystalline structure does. Conversely, 1b shows a clear emission shift, but it retains its molecular arrangement upon grinding.
  • Motoyoshi Noike, Takashi Matsui, Koichi Ooya, Ikuo Sasaki, Shouta Ohtaki, Yoshimitsu Hamano, Chitose Maruyama, Jun Ishikawa, Yasuharu Satoh, Hajime Ito, Hiroyuki Morita, Tohru Dairi
    NATURE CHEMICAL BIOLOGY 11 1 71 - + 2015年01月 [査読有り][通常論文]
     
    Peptide antibiotics are typically biosynthesized by one of two distinct machineries in a ribosome-dependent or ribosome-independent manner. Pheganomycin (PGM (1)) and related analogs consist of the nonproteinogenic amino acid (S)-2-(3,5-dihydroxy-4-hydroxymethyl)phenyl-2-guanidinoacetic acid (2) and a proteinogenic core peptide, making their origin uncertain. We report the identification of the biosynthetic gene cluster from Streptomyces cirratus responsible for PGM production. Unexpectedly, the cluster contains a gene encoding multiple precursor peptides along with several genes plausibly encoding enzymes for the synthesis of amino acid 2. We identified PGM1, which has an ATP-grasp domain, as potentially capable of linking the precursor peptides with 2, and validate this hypothesis using deletion mutants and in vitro reconstitution. We document PGM1's substrate permissivity, which could be rationalized by a large binding pocket as confirmed via structural and mutagenesis experiments. This is to our knowledge the first example of cooperative peptide synthesis achieved by ribosomes and peptide ligases using a peptide nucleophile.
  • Eiji Yamamoto, Satoshi Ukigai, Hajime Ito
    CHEMICAL SCIENCE 6 5 2943 - 2951 2015年 [査読有り][通常論文]
     
    A transition-metal-free method has been developed for the boryl substitution of functionalized aryl-, heteroaryl- and alkenyl halides with a silylborane in the presence of an alkali-metal alkoxide. The base-mediated boryl substitution of organohalides with a silylborane was recently reported to provide the corresponding borylated products in good to high yields, and exhibit good functional group compatibility and high tolerance to steric hindrance. In this study, the scope of this transformation has been extended significantly to include a wide variety of functionalized aryl-, heteroaryl- and alkenyl halides. In particular, the boryl substitution of (E)- and (Z)-alkenyl halides proceeded smoothly to afford the corresponding alkenyl boronates in good to high yields with retention of the configuration using modified reaction conditions. The results of the mechanistic studies suggest that this boryl substitution proceeds via a carbanion-mediated mechanism.
  • Koji Kubota, Eiji Yamamoto, Hajime Ito
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 137 1 420 - 424 2015年01月 [査読有り][通常論文]
     
    The first catalytic enantioselective nucleophilic borylation of a C-O double bond has been achieved. A series of aldehydes reacted with a diboron reagent in the presence of a copper(I)/DTBM-SEGPHOS complex catalyst using MeOH as a proton source to give the corresponding optically active a-alkoxyorganoboronate esters with excellent enantioselectivities. Furthermore, the products could be readily converted to the corresponding functionalized chiral alcohol derivatives through stereospecific C-C bond forming reactions involving the stereogenic C-B bond.
  • Tomohiro Seki, Taichi Ozaki, Takuma Okura, Kiyotaka Asakura, Aya Sakon, Hidehiro Uekusa, Hajime Ito
    CHEMICAL SCIENCE 6 4 2187 - 2195 2015年 [査読有り][通常論文]
     
    In this study, we report the interconvertible tetracolored solid state photoluminescence of gold(I) isocyanide complex 2 upon various external stimuli through solid state structural changes. Soaking complex 2 in acetone yields blue emission as a result of the formation of 2B. The subsequent removal of acetone yields 2G through a crystal-to-crystal phase transition, which exhibits green emission. This green-emitting solid 2G exhibits stepwise emission color changes to yellow and then to orange upon mechanical stimulation by ball-milling, which corresponds to the formation of 2Y and 2O, respectively. 2B could be recovered upon the addition of acetone to 2G, 2Y, and 2O. Thus, these four emitting solid states of 2 can be switched between repeatedly by means of acetone soaking and the application of mechanical stimulation. Importantly, single crystal and powder X-ray diffraction (PXRD) studies fully show the detailed molecular arrangements of 2B, 2G, and 2Y. This is the first mechanochromic compound to show interconvertible four color emission in the solid state. We also present the first example of using PXRD measurements and the Rietveld refinement technique for the structural analysis of a ground powder in a luminescence mechanochromism study. We obtained complete molecular-level structural information of the crystalline states of 2B, 2G, 2Y, and 2O. In comparison with a more solvophobic analogue 1, we suggest that the weak interaction of 2 with acetone in the solid state would allow a solvent inclusion/release mode, which is an important structural factor for the unprecedented multicolor mechanochromic luminescence.
  • Tomohiro Seki, Kenta Sakurada, Mai Muromoto, Hajime Ito
    CHEMICAL SCIENCE 6 2 1491 - 1497 2015年 [査読有り][通常論文]
     
    We report the first photoinduced single-crystal-to-single-crystal (SCSC) phase transition of a gold complex that involves the shortening of intermolecular aurophilic bonds. This is also the first solid state photochromism of a gold complex. Upon UV irradiation, the blue-emitting crystals of the gold(I) isocyanide complex 1 (1B) transform into the weakly yellow-emitting polymorph 1Y. X-ray diffraction analyses reveal that this phase transition proceeds in an SCSC manner. After phase transition from 1B to 1Y, the intermolecular Au...Au separation decreases from 3.5041(14) to 3.2955(6) angstrom, resulting in a red-shifted emission. The photoinduced shortening of the aurophilic bond in the excited state initiates the change in the crystal structure from 1B to 1Y. Moreover, the crystal 1B showed a photosalient effect: the 1B crystals jump upon irradiation with strong UV light owing to the phase transition into 1Y. The aurophilic bond formation in the crystal generates the mechanical movement of the crystal.
  • Eiji Yamamoto, Yuta Takenouchi, Taichi Ozaki, Takanori Miya, Hajime Ito
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 47 16515 - 16521 2014年11月 [査読有り][通常論文]
     
    A new method has been developed for the catalytic asymmetric synthesis of alpha-chiral linear or carbocyclic (gamma-alkoxyallyl)boronates via the copper(I)-catalyzed gamma-boryl substitution of allyl acetals. This reaction afforded the products in high yields with excellent E:Z selectivities and enantioselectivities [only (E)-product, 9198% ee] and also exhibited high functional group compatibility. Subsequent allylation of aldehydes with the alpha-chiral (gamma-alkoxyallyl)boronates provided the anti-1,2-diol derivatives in a highly stereospecific manner, and the utility of the alpha-chiral (gamma-alkoxyallyl)boronates was further demonstrated by a convergent coupling of a complex polyol derivative using a (gamma-alkoxyallyl)boronate and a chiral alpha-oxyaldehyde. The stereoselective modular construction of a complex 3,3-disubstituted cyclopentene containing three consecutive stereocenters including a quaternary chiral carbon was also reported. Useful transformations of the alpha-chiral linear (gamma-alkoxyallyl)boronates were also demonstrated.
  • Takayuki Nakanishi, Yuki Suzuki, Yoshihiro Doi, Tomohiro Seki, Hitoshi Koizumi, Koji Fushimi, Koji Fujita, Yukio Hinatsu, Hajime Ito, Katsuhisa Tanaka, Yasuchika Hasegawa
    INORGANIC CHEMISTRY 53 14 7635 - 7641 2014年07月 [査読有り][通常論文]
     
    The effective magneto optical properties of novel nonanuclear Tb(III) complexes with Tb-O lattice (specifically, [Tb-9(sal-R)(16)(mu-OH)(10)]+NO3-, where sal-R = alkyl salicylate (R = -CH3 (Me), -C2H5 (Et), -C3H7 (Pr), or -C4H9 (Bu)) are reported. The geometrical structures of these nonanudear Tb(III) complexes were characterized using X-ray single-crystal analysis and shape-measure calculation. Optical Faraday rotation was observed in nonanuclear Tb(III) complexes in the visible region. The Verdet constant per Tb(III) ion of the Tb-9(sal-Me) complex is 150 times larger than that of general Tb(III) oxide glass. To understand their large Faraday rotation, electron paramagnetic resonance measurements of Gd(III) complexes were carried out. In this Report, the magneto optical relation to the coordination geometry of Tb ions is discussed.
  • Eiji Yamamoto, Yuta Takenouchi, Koji Kubota, Hajime Ito
    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN 72 7 758 - 769 2014年07月 [査読有り][通常論文]
     
    Transition-metal-catalyzed borylation has emerged as a powerful method for preparation of organoboron compounds, which are useful synthetic reagents in organic synthesis. However, chemo-, regio-, and stereoselective synthesis of the boron compounds are still highly required. Herein, we report copper (I)-catalyzed boryl substitution of allylic carbonates and ethers, monoborylation of 1,3-dienes and enynes, boryl substitution of alkyl halides, and borylative cyclization of alkenes containing an appropriate leaving group for the selective synthesis of various organoboron compounds including allyl- and allenylboronates, and optically active carbocyclic boronates. Preparation of the borylation products has been difficult with known procedures. In addition, direct enantio-convergent transformation of racemic substrates without a racemization or symmetrization process, a novel methodology for asymmetric synthesis with racemic substrates, is also reported.
  • Shiki Yagai, Satoru Okamura, Yujiro Nakano, Mitsuaki Yamauchi, Keiki Kishikawa, Takashi Karatsu, Akihide Kitamura, Akira Ueno, Daiki Kuzuhara, Hiroko Yamada, Tomohiro Seki, Hajime Ito
    NATURE COMMUNICATIONS 5 2014年06月 [査読有り][通常論文]
     
    pi-Conjugated compounds that exhibit tunable luminescence in the solid state under external mechanical stimuli have potential applications in sensors and imaging devices. However, no rational designs have been proposed that impart these mechano-responsive luminescent properties to pi-conjugated compounds. Here we demonstrate a strategy for mechano-responsive luminescent materials by imparting amphiphilic and dipolar characteristics to a luminescent pi-conjugated system. The oligo(p-phenylenevinylene) luminophore with a didodecylamino group at one end and a tri(ethylene glycol) ester group at the other end yields segregated solid structures by separately aggregating its hydrophobic and hydrophilic moieties. The segregated structures force the molecules to align in the same direction, thereby generating a conflict between the side-chain aggregation and dipolar stabilization of the pi-system. Consequently, these metastable solid structures can be transformed through mechanical stimulation to a more stable structure, from a pi-pi stacked aggregate to a liquid crystal and further to a crystalline phase with variable luminescence.
  • Eiji Yamamoto, Kiyotaka Izumi, Yuko Horita, Satoshi Ukigai, Hajime Ito
    TOPICS IN CATALYSIS 57 10-13 940 - 945 2014年06月 [査読有り][通常論文]
     
    Boryl substitution of organohalides with a silylborane and alkoxy bases is described. This reaction can be applied to various functionalized aryl halides. Alkyl and alkenyl halides, and even sterically congested aryl bromides also provided the corresponding borylated products in high yields. Mechanistic studies indicated that neither trace transition-metal impurities nor aryl radical species involved in this reaction.
  • Masaya Sawamura, Hajime Ito
    Copper-Catalyzed Asymmetric Synthesis 157 - 178 2014年03月31日 [査読有り][通常論文]
  • Tomohiko Shirai, Hajime Ito, Yasunori Yamamoto
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 53 10 2658 - 2661 2014年03月 [査読有り][通常論文]
     
    Asymmetric intramolecular direct hydroarylation of -ketoamides gives various types of optically active 3-substituted 3-hydroxy-2-oxindoles in high yields with complete regioselectivity and high enantioselectivities (84-98% ee). This is realized by the use of the cationic iridium complex [Ir(cod)(2)](BAr4F) and the chiral O-linked bidentate phosphoramidite (R,R)-Me-BIPAM.
  • Ikuo Sasaki, Tatsunosuke Amou, Hajime Ito, Tatsuo Ishiyama
    ORGANIC & BIOMOLECULAR CHEMISTRY 12 13 2041 - 2044 2014年 [査読有り][通常論文]
     
    The development of an Ir-catalyzed ortho-C-H borylation of aromatic aldimines derived from pentafluoroaniline is reported. This reaction proceeded at 120 degrees C to afford the corresponding borylated products in high yield with good regioselectivity using an Ir complex formed in situ from [Ir(OMe)(cod)](2)/2(C6F5)(3)P in the presence of 2-norbornene.
  • Tatsuo Ishiyama, Takeaki Saiki, Emi Kishida, Ikuo Sasaki, Hajime Ito, Norio Miyaura
    ORGANIC & BIOMOLECULAR CHEMISTRY 11 47 8162 - 8165 2013年12月 [査読有り][通常論文]
     
    Aromatic C-H silylation of neat arenes with 1-hydrosilatrane was found to be efficiently catalyzed by iridium catalysts composed of 1/2[Ir(OMe)(cod)]2 and 2,9-dimethyl-1,10-phenanthroline at 120 degrees C to afford the corresponding silylated products in high yields. The silylated products can be used for the Hiyama cross-coupling reaction.
  • Tomohiro Seki, Kenta Sakurada, Hajime Ito
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 52 49 12828 - 12832 2013年12月 [査読有り][通常論文]
  • Yasuchika Hasegawa, Tomoki Ohkubo, Takayuki Nakanishi, Atsushi Kobayashi, Masako Kato, Tomohiro Seki, Hajime Ito, Koji Fushimi
    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 2013 34 5911 - 5918 2013年12月 [査読有り][通常論文]
     
    The effect of ligand polarization on the formation of strongly luminescent lanthanide complexes with asymmetric structures is described for the first time. The lanthanide complexes are composed of Eu-III ions, three hexafluoroacetylacetonate (hfa) ligands, and two monodentate phosphine oxide ligands, namely, triphenylphosphine oxide (TPPO), p-tolyldiphenylphosphine oxide (TPPO-Me), tri-p-tolylphosphine oxide (TPPO-3Me) or o-phenoxyphenyldiphenylphosphine oxide (TPPO-OPh). The luminescence properties of the Eu-III complexes are characterized by their emission quantum yields, emission lifetimes, and their radiative (k(r)) and nonradiative (k(nr)) rate constants. The Eu-III complex with TPPO-OPh ligands offers a markedly high emission quantum yield (72% in [D-6]acetone, 85% in the solid state) owing to enhancement of the electric dipole transition and suppression of vibrational relaxation, which are directly related to k(r) and k(nr). The coordination geometries of the Eu-III complexes are categorized by shape-measure calculations. The Eu-III complexes exhibit characteristic square-antiprismatic or trigonal-dodecahedral structures, depending on the ligand polarization. Strongly luminescent Eu(hfa)(3)(TPPO-OPh)(2) has an asymmetric dodecahedron structure. The formation of distorted dodecahedral structures with low vibrational frequencies for the enhancement of luminescence is elucidated in terms of the ligand polarization of the monodentate phosphine oxide ligands in the Eu-III complexes.
  • Koji Kubota, Eiji Yamamoto, Hajime Ito
    ADVANCED SYNTHESIS & CATALYSIS 355 18 3527 - 3531 2013年12月 [査読有り][通常論文]
     
    An asymmetric monoborylation of alkenylsilanes catalyzed by a copper(I) complex with the chiral bisphosphine ligand BenzP* is reported. The reaction proceeded with excellent regioselectivity and high enantioselectivity to afford the corresponding optically active organoboronate esters with a stereogenic CB bond containing a vicinal silyl group. The synthetic utility of the product is demonstrated through stepwise transformations to multifunctional optically active compounds in a stereospecific manner.
  • Tomohiro Seki, Sayaka Kurenuma, Hajime Ito
    CHEMISTRY-A EUROPEAN JOURNAL 19 48 16214 - 16220 2013年11月 [査読有り][通常論文]
     
    We report the luminescent color tuning of a new complex, 2-benzothiophenyl(4-methoxyphenyl isocyanide)gold(I) (1), by using a new polymorph doping approach. The slow crystallization of the complex 1 afforded three different pure polymorphic crystals with blue, green, and orange emission under UV-light irradiation. The crystal structures of pure polymorphs of 1 were investigated in detail by means of single-crystal X-ray analyses. Theoretical calculations based on the single-crystal structures provided qualitative explanation of the difference in the excited energy-levels of the three polymorphs of 1. In sharp contrast, the rapid precipitation of 1, with the optimized conditions reproducibly afforded homogeneous powder materials showing solid-state white-emission with Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinates of (0.33, 0.35), which is similar to pure white. New polymorphic doping has been revealed to be critical to this white emission through spectroscopic and X-ray diffraction analyses. The coexistence of the multiple polymorphs of 1 within the homogeneous powder materials and the ideal mixing of multiple luminescent colors gave its white emission accompanied with energy transfer from the predominant green-emitting polymorph to the minor orange-emitting polymorph.
  • Shohei Sakashita, Miho Takizawa, Juugaku Sugai, Hajime Ito, Yasunori Yamamoto
    ORGANIC LETTERS 15 17 4308 - 4311 2013年09月 [査読有り][通常論文]
     
    Palladium-catalyzed Suzuki-Miyaura cross-coupling reactions of tetrabutylammonium 2-pyridyltriolborate salts with various aryl (heteroaryl) chlorides can produce the corresponding desired coupling products with good to excellent yields. These tetrabutylammonium salts are more reactive than the corresponding lithium salts. The coupling reactions with aryl chlorides progressed in the presence of PdCl(2)dcpp (3 mol %) and Cul/MeNHCH2CH2OH (20 mol %) in anhydrous DMF without bases.
  • Hajime Ito, Mai Muromoto, Sayaka Kurenuma, Shoji Ishizaka, Noboru Kitamura, Hiroyasu Sato, Tomohiro Seki
    NATURE COMMUNICATIONS 4 2013年06月 [査読有り][通常論文]
     
    Numerous studies have focused on the mechanical control of solid structures and phase changes in molecular crystals. However, the molecular-level understanding of how macroscopic forces affect the molecules in a solid remains incomplete. Here we report that a small mechanical stimulus or solid seeding can trigger a single-crystal-to-single-crystal transformation from a kinetically isolated polymorph of phenyl(phenyl isocyanide) gold(I) exhibiting blue photoluminescence to a thermodynamically stable polymorph exhibiting yellow emission without the need for heating or solvent. The phase transformation initiates at the location of the mechanical stimulation or seed crystal, extends to adjacent crystals, and can be readily monitored visually by the accompanying photoluminescent colour change from blue to yellow. The transformation was characterized using single crystal X-ray analysis. Our results suggest that the transformation proceeds through self-replication, causing the complex to behave as 'molecular dominoes'.
  • Koji Kubota, Eiji Yamamoto, Hajime Ito
    Journal of the American Chemical Society 135 7 2635 - 2640 2013年02月20日 [査読有り][通常論文]
     
    A borylative exo-cyclization of alkenyl halides has been reported. The reaction includes the regioselective addition of a borylcopper(I) intermediate to unactivated terminal alkenes, followed by the intramolecular substitution of the resulting alkylcopper(I) moiety for the halide leaving groups. Experimental and theoretical investigations of the reaction mechanism have also been described. This reaction provides a new method for the synthesis of alkylboronates containing strained cycloalkyl structures from simple starting materials. © 2013 American Chemical Society.
  • Yasunori Yamamoto, Kazuya Ikizakura, Hajime Ito, Norio Miyaura
    MOLECULES 18 1 430 - 439 2013年01月 [査読有り][招待有り]
     
    We newly developed lithium methyltriolborate as an air-stable white solid that is convenient to handle. The good performance of this triolborate for metal-catalyzed bond-forming reactions was demonstrated in palladium-catalyzed cross-coupling reactions with haloarenes. Cross-coupling reaction of [MeB(OCH2)(3)CCH3]Li with aryl halides occurred in the presence of Pd(OAc)(2)/RuPhos complex in refluxing MeOH/H2O and the absence of bases.
  • Ikuo Sasaki, Hana Doi, Toshiya Hashimoto, Takao Kikuchi, Hajime Ito, Tatsuo Ishiyama
    CHEMICAL COMMUNICATIONS 49 68 7546 - 7548 2013年 [査読有り][通常論文]
     
    Ir(I)-catalyzed C-H borylation of 1-cycloalkenecarboxylic derivatives with bis(pinacolato)diboron affords various alkenylboronates with functional groups in excellent yields. This reaction was also used in a one-pot borylation/Suzuki-Miyaura cross-coupling procedure.
  • Kohsuke Kawaguchi, Tomohiro Seki, Takashi Karatsu, Akihide Kitamura, Hajime Ito, Shiki Yagai
    CHEMICAL COMMUNICATIONS 49 97 11391 - 11393 2013年 [査読有り][通常論文]
     
    A cholesterol-functionalized gold(I)-isocyanide complex exhibiting mechanochromic luminescence properties was self-organized into distinct microscopic structures with different photoluminescence properties through vapor-diffusion of a poor solvent into its dichloromethane solution. The structure-optical property relationship of these microstructures could be related to the mechanically induced phase transition.
  • Ito Hajime, Seki Tomohir
    Bulletin of Japan Society of Coordination Chemistry 62 3 - 11 2013年 [査読有り][通常論文]
  • Eiji Yamamoto, Kiyotaka Izumi, Yuko Horita, Hajime Ito
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 134 49 19997 - 20000 2012年12月 [査読有り][通常論文]
     
    An unexpected borylation of organic halides with a silyborane in the presence of an alkoxy base has been observed. This formal nucleophilic boryl substitution can be applied to a broad range of substrates with high functional group compatibility. Even sterically hindered aryl bromides afforded the corresponding boryl compounds in high yields. Preliminary mechanistic studies indicated that this boryl substitution is promoted by neither transition-metal contamination nor a radical-mediated process.
  • Yasunori Yamamoto, Masaaki Yohda, Tomohiko Shirai, Hajime Ito, Norio Miyaura
    CHEMISTRY-AN ASIAN JOURNAL 7 10 2446 - 2449 2012年10月 [査読有り][通常論文]
     
    A chiral O-linked C2-symmetric bidentate phosphoramidite (Me-BIPAM) was found to be efficient for the ruthenium-catalyzed addition of arylboronic acids to isatins. Asymmetric synthesis of 3-aryl-3-hydroxy-2-oxindoles by 1,2-addition of arylboronic acids to isatins was carried out in the presence of [RuCl2(PPh3)3]/(R,R)-Me-BIPAM and KF, resulting in an enantioselectivity as high as 90?% ee. It was found that the reaction with N-protected isatins proceeds with high yields and good enantioselectivities. The best protective groups on the nitrogen atom were different depending on the substituents on the aromatic ring. The use of a N-benzyl group resulted in excellent enantioselectivities in many substrates compared with other groups.
  • Hajime Ito
    NATURE CHEMISTRY 4 6 438 - 439 2012年06月 [査読有り][通常論文]
  • Hajime Ito, Takanori Miya, Masaya Sawamura
    TETRAHEDRON 68 17 3423 - 3427 2012年04月 [査読有り][通常論文]
     
    We have developed a useful procedure for borylation using catalytic CuCl/Xantphos and stoichiometric K(O-t-Bu): the highly versatile method is suitable for the synthesis of allylboronates including those with terminal and internal allylic systems, cyclic structures, and functional groups. Optically active allylboronates were synthesized from prochiral substrates with a chiral diphosphine ligand using this procedure. The reaction rate is generally higher than the original Cu(O-t-Bu)/ligand catalyst system, which we previously reported. (C) 2011 Elsevier Ltd. All rights reserved.
  • Hajime Ito, Yuko Horita, Masaya Sawamura
    ADVANCED SYNTHESIS & CATALYSIS 354 5 813 - 817 2012年03月 [査読有り][通常論文]
     
    We report the first copper(I)-catalyzed reaction between a disilane and allylic carbonates to produce allylsilanes. The silyl nucleophilic substitution proceeded primarily in a SN2 fashion whereas SN2' products were also obtained through s-p-s isomerization of the copper(III) intermediate depending on the substrates steric bulk.
  • Hajime Ito, Koji Kubota
    ORGANIC LETTERS 14 3 890 - 893 2012年02月 [査読有り][通常論文]
     
    Borylation of alkyl halides with diboron proceeded in the presence of a copper(I)/Xantphos catalyst and a stoichiometric amount of K(O-t-Bu) base. The boryl substitution proceeded with normal and secondary alkyl chlorides, bromides, and iodides, but alkyl sulfonates did not react. Menthyl halides afforded the corresponding borylation product with excellent diastereoselectivity, whereas (R)-2-bromo-5-phenylpentane gave a racemic product. Reaction with cyclopropylmethyl bromide resulted in ring-opening products, suggesting the reaction involves a radical pathway.
  • Hajime Ito, Yuko Horita, Eiji Yamamoto
    CHEMICAL COMMUNICATIONS 48 64 8006 - 8008 2012年 [査読有り][通常論文]
     
    The regio- and diastereoselective silaboration of aromatic alkenes with a silylboron compound proceeds in the presence of a catalytic amount of potassium tert-butoxide, providing a complementary method to the corresponding transition metal-catalyzed reactions.
  • Yusuke Sasaki, Masaya Sawamura, Hajime Ito
    CHEMISTRY LETTERS 40 9 1044 - 1046 2011年09月 [査読有り][通常論文]
     
    The reaction of enantioenriched allenylboronate 3a (98% ee) with benzaldehyde gave homopropargylic alcohol syn- and anti-4b with anomalous syn addition selectivity (anti:syn = 29:71) and high cc (98% and 97%, respectively). The stereochemical outcome in terms of the absolute configuration shows that this reaction proceeds through a cyclic transition state. Density functional theoretical (DFT) calculations were carried out to elucidate the mechanism of this anomalous syn-selectivity.
  • 伊藤 肇
    Synthesiology 4 3 157 - 165 National Institute of Advanced Industrial Science and Technology 2011年 
    自動車用ナビゲーションは、電子技術の急速な発展を背景として、目的地に効率的に行きたいというニーズが自動車開発の企画にのり、搭載する多くの技術、通信や道路データ等支える多くの技術が長年にわたる官学民の協力で実現し、普及してきた。またそれらの技術はITS標準化の名の下に国際的な整合が行われている。なかでもナビゲーションは運転中の視認・操作を伴う車載装置でもあり、安全性、特にヒューマンファクタが重要なアイテムになる。この論文は開発の歴史を紐解き、社会受容が可能になるヒューマンファクタの研究と標準化を紹介する。
  • Yusuke Sasaki, Yuko Horita, Chongmin Zhong, Masaya Sawamura, Hajime Ito
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 50 12 2778 - 2782 2011年 [査読有り][通常論文]
  • Hajime Ito, Shun Kunii, Masaya Sawamura
    NATURE CHEMISTRY 2 11 972 - 976 2010年11月 [査読有り][通常論文]
     
    Asymmetric reactions that transform racemic mixtures into enantio-enriched products are in high demand, but classical kinetic resolution produces enantiopure compounds in <50% yield even in an ideal case. Many deracemization processes have thus been developed including dynamic kinetic resolution and dynamic kinetic asymmetric transformation, which can provide enantio-enriched products even after complete conversion of the racemic starting materials. However, these dynamic processes require racemization or symmetrization of the substrates or intermediates. We demonstrate a direct chemical enantio-convergent transformation without a racemization or symmetrization process. Copper(I)-catalysed asymmetric allylic substitution of a racemic allylic ether afforded a single enantiomer of an a-chiral allylboronate with complete conversion and high enantioselectivity (up to 98% enantiomeric excess). One enantiomer of the substrate undergoes an anti-S(N)2'-type reaction whereas the other enantiomer reacts via a syn-S(N)2' pathway. The products, which cannot be prepared by dynamic procedures, have been used to construct all-carbon quaternary stereocentres.
  • Chongmin Zhong, Shun Kunii, Yuki Kosaka, Masaya Sawamura, Hajime Ito
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 132 33 11440 - 11442 2010年08月 [査読有り][通常論文]
     
    A new asymmetric route for the synthesis of trans-2-aryl- and -heteroaryl-substituted cyclopropylboronates has been developed. (Z)-3-arylallylic phosphates were converted to the optically active products with high yield and diastereo- and enantioselectivity through a copper(I)-catalyzed reaction with a diboron derivative. Under mild reaction conditions, the reaction affords the arylcyclopropane products with a functional group and a heteroaromatic group in a highly enantioselective manner. When (E)-allylic phosphates were used as substrates, a ligand-controlled product switch between the trans and cis configurations was observed.
  • Hajime Ito, Takashi Toyoda, Masaya Sawamura
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 132 17 5990 - + 2010年05月 [査読有り][通常論文]
     
    A copper(I)-catalyzed stereospecific reaction for the preparation of cis- and trans-1-silyl-2-borylcyclobutanes as well as 1-phenyl-2-borylcyclobutanes is reported. (Z)- and (E)-Homoallylic methanesulfonates were converted to the corresponding trans- and cis-cyclobutane derivatives, respectively, in the presence of a CuCl/dppp catalyst, bis(pinacolato)diboron, and K(O-t-Bu)/THF. Stereospecific derivatizations of the cis- and trans-borylcyclobutanes were carried out to demonstrate the utility of the borylcyclobutanes.
  • Yusuke Sasaki, Chongmin Zhong, Masaya Sawamura, Hajime Ito
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 132 4 1226 - + 2010年02月 [査読有り][通常論文]
     
    Copper(I)-catalyzed asymmetric monoborylation of 1,3-dienes has been developed. We describe the production of either optically active homoallyl- or allylboronates with high regio- and enantioselectivity (88-97% ee) through monoborylation of 1,3-dienes. The reaction with 1,3-cyclohexadiene derivatives afforded the corresponding enantioenriched homoallyboronates. By simply changing the reaction conditions, a drastic change of product preference between homoallyl- and allylboronates was found in the reaction of 1,3-cyclopentadiene and 1,3-cycloheptadiene.
  • Hajime Ito, Takuma Okura, Kou Matsuura, Masaya Sawamura
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 49 3 560 - 563 2010年 [査読有り][通常論文]
  • Hajime Ito, Tomohisa Saito, Takahiro Miyahara, Chongmin Zhong, Masaya Sawamura
    ORGANOMETALLICS 28 16 4829 - 4840 2009年08月 [査読有り][通常論文]
     
    Gold hydride is a rare transition-metal species. Despite the fact that gold hydrides may be key intermediates in several gold-catalyzed reactions, their chemical properties are not well understood. We report the synthesis, characterization, and catalytic properties of gold(I) hydride species that play an important role in a gold(I)-catalyzed dehydrogenative alcohol silylation. Tricoordinated complexes AuCl(xantphos) (1a) and AuCl(xy-xantphos) (1b) were prepared and characterized by (1)H and (31)P{(1)H} NMR measurements and X-ray crystallography. Gold(I) hydride species 6b generated from the reaction between 1b and PhMe(2)SiH (4b) in CDCl(3) was characterized by (1)H and (31)P NMR measurements and ESI-MS spectrometry. NMR and kinetic studies reveald that the reaction mechanism involves the gold(I) hydride species as a key intermediate. The high catalytic activities of 1a and 1b in dehydrogenative alcohol silylation are explained by the stability of the tricoordinated chelating structure and the activation of the Au-Cl bond induced by the stereoelectronic effect of the coordinating phosphorus atoms. This study reports the first example of a gold(I) hydride complex that exhibits catalytic activity.
  • Chongmin Zhong, Yusuke Sasaki, Hajime Ito, Masaya Sawamura
    CHEMICAL COMMUNICATIONS 39 5850 - 5852 2009年 [査読有り][通常論文]
     
    Cu(I)-catalyzed anti-S(N)2'-type reduction of internal propargylic carbonates with hydrosilanes affords various di- and trisubstituted allenes with high regioselectivities; the reactions are compatible with functional groups and work efficiently for the synthesis of optically-active allenes.
  • Ito H
    Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry 66 12 1168 - 1177 2008年12月 [査読有り][通常論文]
     
    New fundamental reactions of organometallic compounds can often be a rich source of new synthetic reactions. We found sigma-bond metathesis of M-X bonds in group 11 metal compounds with Si-H, Si-Si and B-B bonds. Through these reactions, several intermediates such as borylcopper(I), silylcopper(I), gold(I) hydride species, which otherwise are not easily accessible, can be generated and incorporated into catalytic reactions. We report a novel and versatile method for the synthesis of allylboronates through gamma-selective substitution of allylic carbonates with diboron in the presence of a Cu(I)-phosphine catalyst. The Cu(I)-catalyzed reaction includes formal nucleophilic reaction of borylcopper(I) intermediates to allylic carbonates. The approach involving the reaction of borylcopper(I) intermediates has been further expanded to enantioselective synthesis of both optically active alpha-chiral allylboronates and B, Si-bifunctional cyclopropanes. Copper(I) catalysis based on sigma-bond metathesis of hydrosilanes and disilanes with copper(I) complex offers new synthetic methods for various organosilanes. Gold(I) catalysis involving gold(I) hydride species is also reported.
  • Hajime Ito, Yusuke Sasaki, Masaya Sawamura
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 47 15774 - + 2008年11月 [査読有り][通常論文]
     
    A versatile synthetic method for the preparation of the allenylboronates, Cu(I)-catalyzed reaction of propargylic carbonates with a diboron, is described. A Cu(O-t-Bu)-Xantphos catalyst system was effective for the preparation of various allenylboron compounds, allenylboronates with different substitution patterns, those with functional groups, and an axially chiral one. The Lewis acid promoted stereoselective addition to aldehydes leading to homopropargylic alcohols showed the usefulness of the new allenylboronates.
  • Yohsuke Asano, Hajime Ito, Kenji Hara, Masaya Sawamura
    ORGANOMETALLICS 27 22 5984 - 5996 2008年11月 [査読有り][通常論文]
     
    The addition of terminal alkynes to aromatic aldehydes was carried out in t-BuOH under mild conditions in the presence of a Cu-phosphine complex, which was prepared in situ from Cu(O-t-Bu) and TRAP chiral bisphosphine, to yield enantiomerically enriched propargyl alcohols with moderate enantioselectivities. Studies on the screening of various ligands showed that wide bite angles of bisphosphine ligands are important for the Cu catalysis. According to the analysis of stoichiometric reactions, the reaction presumably involves the nucleophilic addition of a TRAP-coordinated Cu(I) acetylide to an aldehyde: The alcoholic solvent participates in the addition through coordination to the Cu center and simultaneous protonation of the carbonyl oxygen. The C-C bond-forming addition step is reversible with a strong preference for the backward reaction.
  • Ito H, Saito T, Oshima N, Kitamura N, Ishizaka S, Hinatsu Y, Wakeshima M, Kato M, Tsuge K, Sawamura M
    Journal of the American Chemical Society 130 31 10044 - + 2008年08月 [査読有り][通常論文]
     
    Reversible mechanotronic luminescence of [(C(6)F(5)Au)(2)(mu-1,4-diisocyanobenzene)] is reported. Grinding of the complex induced a photoluminescent color change, which was restored by exposure to a solvent. This cycle was repeated 20 times with no color degradation in the emissions. Their optical properties, X-ray crystallographic analysis, IR, and XRD measurements strongly suggested that the change in the molecular arrangement is responsible for this mechanochromic property. Intermolecular aurophilic bondings presumably play a key role in the altered emission.
  • Hajime Ito, Shinichiro Ito, Yusuke Sasaki, Kou Matsuura, Masaya Sawamura
    PURE AND APPLIED CHEMISTRY 80 5 1039 - 1045 2008年05月 [査読有り][通常論文]
     
    Copper-catalyzed gamma-selective substitution of allylic carbonates with diboron provides a new method for the efficient synthesis of allylboronates. Optically active a-chiral allylboronates were synthesized through the reaction of chiral allylic carbonates with bis(pinacolato)diboron in the presence of achiral Cu(I)-catalyst with highly efficient chirality transfer. Additionally, in the presence of a chiral Cu(I) catalyst, optically active alpha-chiral allylboronates were obtained with >90 % ee through the reaction of prochiral substrates with the diboron.
  • Hajime Ito, Yuki Kosaka, Kousuke Nonoyama, Yusuke Sasaki, Masaya Sawamura
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 47 39 7424 - 7427 2008年 [査読有り][通常論文]
  • Ito H, Ito S, Sasaki Y, Matsuura K, Sawamura M
    Journal of the American Chemical Society 129 48 14856 - + 2007年12月 [査読有り][通常論文]
     
    A method for the synthesis of alpha-chiral allylboronates featuring the Cu(I)-catalyzed enantioselective substitution of readily available allylic carbonates with a diboron is described. Using this method, various alpha-chiral allylboronates, including functionalized allylboronates, were successfully synthesized, with high enantiomeric purity.
  • Hajime Ito, Tsuyoshi Maeda, Masaya Sawamura
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 80 10 1981 - 1986 2007年10月 [査読有り][通常論文]
     
    A new tetranuclear platinum(II) metallamacrocycle, including four 1,3-diisocyanoarene ligands, was synthesized and characterized. The reaction Of PtI2(cod) with an equimolar amount of the 1,3-diisocyanoarene ligand in dichloromethane under diluted conditions gave the metallamacrocycle [(PtI2)(4)(1,3-diisocyanoarene)(4)], X-ray crystallographic analysis showed that the complex adopted a square ring structure with trans arrangement of coordinated isocyanides around the Pt atoms. GPC, ESI-MS, IR, and NMR analysis of the metallamacrocycle showed that the tetranuclear macrocyclic scaffold was maintained in solution.
  • Yohsuke Asano, Kenji Hara, Hajime Ito, Masaya Sawamura
    ORGANIC LETTERS 9 20 3901 - 3904 2007年09月 [査読有り][通常論文]
     
    The addition of terminal alkynes to aromatic aldehydes was carried out under mild conditions in the presence of a Cu-phosphine complex, which was prepared in situ from Cu(O-t-Bu) and TRAP chiral bisphosphine, to yield enantiomerically enriched propargyl alcohols with moderate enantioselectivities. Furthermore, according to stoichiometric reactions, the reaction presumably involves the addition of a TRAP-coordinated Cu(l) acetylide to an aldehyde.
  • Hajime Ito, Takayuki Kato, Masaya Sawamura
    CHEMISTRY-AN ASIAN JOURNAL 2 11 1436 - 1446 2007年 [査読有り][通常論文]
     
    New isocyanide ligands with meta-terphenyl backbones were synthesized. 2,6-Bis[3,5-bis(trimethylsilyl)-phenyl]-4-methylphenyl isocyanide exhibited the highest rate acceleration in rhodium-catalyzed hydrosilylation among other isocyanide and phosphine ligands tested in this study. H-1 NMR spectroscopic studies on the coordination behavior of the new ligands to [Rh(cod)(2)]BF4 indicated that 2,6-bis-[3,5-bis(trimethylsilyl)phenyl]-4-methylphenyl isocyanide exclusively forms the biscoordinated rhodium-isocyanide complex, whereas less sterically demanding isocyanide ligands predominantly form tetracoordinated rhodium-isocyanide complexes. FTIR and C-13 NMR spectroscopic studies on the hydrosilylation reaction mixture with the rhodium-isocyanide catalyst showed that the major catalytic species responsible for the hydrosilylation activity is the Rh complex coordinated with the isocyanide ligand. DFT calculations of model compounds revealed the higher affinity of isocyanides for rhodium relative to phosphines. The combined effect of high ligand affinity for the rhodium atom and the bulkiness of the ligand, which facilitates the formation of a catalytically active, monoisocyanide-rhodium species, is proposed to account for the catalytic efficiency of the rhodium-bulky isocyanide system in hydrosilylation.
  • Hajime Ito, Takayuki Kato, Masaya Sawamura
    CHEMISTRY LETTERS 35 9 1038 - 1039 2006年09月 [査読有り][通常論文]
     
    Bulky isocyanide ligands having meta-terphenyl backbone were developed. Their usefulness as a supporting ligand in catalysis was illustrated by the application to the rhodium-catalyzed hydrosilylation of cyclohexanone. The combined effect of the high ligand affinity to the rhodium atom and the ligand bulkiness to facilitate the formation of a catalytically active, monoligated isocyanide-rhodium species was proposed.
  • A Ochida, S Ito, T Miyahara, H Ito, M Sawamura
    CHEMISTRY LETTERS 35 3 294 - 295 2006年03月 [査読有り][通常論文]
     
    A series of silicon-constrained monodentate trialkylphosphines SMAPs bearing a Si substituent with diverse electronic natures were synthesized. DFT calculations and NMR measurements indicated that these compounds constitute a class of electronically tunable trialkylphosphines. The tunable range of donor power overlaps those of tri(tert-butyl)phosphiiie and monoalkyldiarylphosphines.
  • Y. Mizobe, N. Tohnai, H. Ito, M. Miyata, Y. Hasegawa
    Chem. Commun. 20 2126 - 2128 2006年 [査読有り][通常論文]
     
    Solid-state fluorescence enhancement was achieved by preparation of rigid packing that was afforded by disposition of benzylamine into tubulate spaces, serving as a powerful and useful strategy for the enhancement.
  • Ito H, Kawakami C, Sawamura M
    Journal of the American Chemical Society 127 46 16034 - 16035 2005年11月 [査読有り][通常論文]
  • H Ito, K Takagi, T Miyahara, M Sawamura
    ORGANIC LETTERS 7 14 3001 - 3004 2005年07月 [査読有り][通常論文]
     
    A gold(I) complex of Xantphos AuCl(xantphos) catalyzes the dehydrogenative silylation of alcohols with high chemoselectivity and solvent tolerance. It is selective for the silylation of hydroxyl groups in the presence of alkenes, alkynes, alkyl halides (RCl, RBr), ketones, aldehydes, conjugated enones, esters, and carbamates.
  • H Ito, A Watanabe, M Sawamura
    ORGANIC LETTERS 7 9 1869 - 1871 2005年04月 [査読有り][通常論文]
     
    Cu(I) complexes of xanthane-based diphosphines were versatile catalysts for dehydrogenative alcohol silylation, exhibiting high activity and broad substrate scope. Highly selective silylation of 1-decanol over 2-decanol is possible even with a silylating reagent of small steric demand such as HSiMe2Ph or HSiEt3.
  • A Ochida, K Hara, H Ito, M Sawamura
    ORGANIC LETTERS 5 15 2671 - 2674 2003年07月 [査読有り][通常論文]
     
    [GRAPHICS] A new trialkylphosphine ligand with Me3P-like steric and electronic properties, 4-phenyl-1-phospha-4-silabicyclo[2.2.2]octane (Ph-SMAP), was synthesized. Given a phenyl group at the silicon atom, the Ph-SMAP ligand displayed nonvolatility with retention of Me3P-like properties. The new ligand was air-stable, crystalline, and easy to handle.
  • H Ito, H Yamanaka, T Ishizuka, J Tateiwa, A Hosomi
    SYNLETT 4 479 - 482 2000年04月 [査読有り][通常論文]
     
    Aromatic ketones and olefins were selectively converted to the corresponding alcohols and alkanes by a reagent prepared from a copper(I) salt and a hydrosilane. Excess use of the hydrosilane is most important to attain the high reactivities. One-electron transfer process as well as nucleophilic reaction of hydride would contribute to the selectivity.
  • H Ito, A Hosomi
    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN 58 4 274 - 284 2000年04月 [査読有り][通常論文]
     
    This article presents several synthetic reactions by using a catalyst containing group 11 metals. We recently found an unprecedented reaction between an alkynylsilane and CuCl to produce the corresponding alkynylcopper(I) in DMI (1,3-dimethyl-2-imidazolidinone). This transformation was applied to the synthesis of alkynyl ketones catalyzed by CuCl. A new and convenient procedure for the stereo- and chemoselective reduction of carbonyl compounds by use of a complex of copper(I) hydride generated from a hydrosilane and a copper(I) salt is described. A new method for the synthesis of enol esters (O-acylated products) from silyl enol ethers by use of a copper(I) salt is also described. An unprecedented cleavage reaction of the silicon-silicon bond in a disilane with a Cu(I) salt and its new 1,4-addition reaction toward alpha,beta-unsaturated carbonyl compounds in the presence of a catalytic amount of a Cu(I) salt is reported. Thus under these conditions, organosilyl-, hydrido-, alkynyl-, aryl- and heteroarylsilanes were smoothly converted to the corresponding organocopper reagents. Similarly, Au(I) complexes efficiently catalyze the dehydrogenative dimerization of trialkylstannanes and hydrosilylation of aldehydes. The present method provides new synthetic tools.
  • H Ito, T Yajima, J Tateiwa, A Hosomi
    CHEMICAL COMMUNICATIONS 11 981 - 982 2000年 [査読有り][通常論文]
     
    The first examples of the hydrosilylation of organic compounds such as aldehydes and an aldimine using a catalytic amount of a gold complex, which accomplished versatile regio- and chemo-selective reduction of carbonyl compounds, are described.
  • H Ito, T Yajima, J Tateiwa, A Hosomi
    TETRAHEDRON LETTERS 40 44 7807 - 7810 1999年10月 [査読有り][通常論文]
     
    This paper describes an unprecedented catalytic reaction using Au(I) complexes. Au complexes efficiently catalyze dehydrogenative dimerization of trialkylstannanes. Catalytic activity of the Au(I) complex toward dehydrogenative dimerization of the trialkylstannane is extremely high (0.1 mol%, 48 h) comparable to that of Pd catalysts. The synthetic generality of this reaction was demonstrated for the reaction using tributyl-, trioctyl-, triphenylstannane. (C) 1999 Elsevier Science Ltd. All rights reserved.
  • H Ito, T Ishizuka, T Okumura, H Yamanaka, J Tateiwa, M Sonoda, A Hosomi
    JOURNAL OF ORGANOMETALLIC CHEMISTRY 574 1 102 - 106 1999年02月 [査読有り][通常論文]
     
    Highly stereoselective metathesis reactions between optically active silyl compounds and copper(I) salts in 1,3-dimethyl-2-imidazolidinone (DMI) are reported. The substitution reaction of (+)-alpha-naphthylphenylmethylsilane with a mixture of lithium tert-butoxide and copper(I) salt smoothly proceeded in DMI to give the corresponding silyl ether with a high degree of retention of the configuration in a quantitative yield. The use of DMI as a solvent and the presence of a chloride ion are necessary for this reaction. An optically active alkynylsilane also reacted with the mixed reagent to afford the corresponding silyl ether. A mechanism of oxidative addition of the hydrosilane and reductive elimination of the silyl ether on copper is proposed. (C) 1999 Elsevier Science S.A. All rights reserved.
  • H Ito, Y Ujita, J Tateiwa, M Sonoda, A Hosomi
    CHEMICAL COMMUNICATIONS 22 2443 - 2444 1998年11月 [査読有り][通常論文]
     
    An intramolecular hydrogen bond promotes rate enhancement in both the allylation and the reduction of carbonyl compounds and also regioselective allylation.
  • Ito H, Ishizuka T, Tateiwa J.-I, Sonoda M, Hosomi A
    Journal of the American Chemical Society 120 43 11196 - 11197 1998年11月 [査読有り][通常論文]
  • H Ito, T Ishizuka, J Tateiwa, A Hosomi
    TETRAHEDRON LETTERS 39 35 6295 - 6298 1998年08月 [査読有り][通常論文]
     
    A new selective synthetic method of enol esters (O-acylated products) from silyl enol ether and acid chloride in the presence of CuCl is described. This reaction proceeds smoothly in DMI (1,3-dimethyl-2-imidazolidinone) but not in a less polar solvent. The silicon-copper exchange reaction pathway is proposed for this transformation as in the cases of hydrosilane and alkynylsilane which were previously reported. (C) 1998 Elsevier Science Ltd. All rights reserved.
  • Miura K, Sato H, Tamaki K, Ito H, Hosomi A
    Tetrahedron Letters 39 17 2585 - 2588 1998年04月 [査読有り][通常論文]
     
    Dimethylsilyl enolates and alpha-dimethylsilyl esters reacted with aldehydes in N,N-dimethyl-formamide without an activator to give aldol adducts in moderate to good yields. Under the same conditions, the corresponding trimethylsilyl derivatives exhibited lower reactivities toward the aldol reaction. (C) 1998 Elsevier Science Ltd. All rights reserved.
  • Hojo M, Murakami C, Ohno K, Kuboyama J, Nakamura S.-Y, Ito H, Hosomi A
    Heterocycles 47 1 97 - 100 1998年01月 [査読有り][通常論文]
     
    Alkenes are oxidatively dichlorinated by stirring with manganese(II) chloride-lithium methoxide under oxygen atmosphere, followed by treatment with cone. hydrochloric acid. This di-functionalization of alkenes can be applied to the chlorolactonization of lithium 4-pentenoates.
  • M Murakami, Y Hoshino, H Ito, Y Ito
    CHEMISTRY LETTERS 2 163 - 164 1998年 [査読有り][通常論文]
     
    A new synthetic method of N-methoxy-N-methylamides is developed. The palladium-catalyzed coupling reaction of N-methoxy-N-methylcarbamoyl chloride furnished N-methoxy-N-methylamide in moderate to good yield, wherein a carbonyl equivalent was appended to sp and sp(2) carbon atoms as a versatile synthetic basis for further manipulation.
  • H Ito, T Ishizuka, K Arimoto, K Miura, A Hosomi
    TETRAHEDRON LETTERS 38 51 8887 - 8890 1997年12月 [査読有り][通常論文]
     
    Hydride transfer from a hydrosilane to a copper(I) salt is reported. The silicon group of hydrosilanes was smoothly replaced by copper(I) chloride in DMI to give the corresponding metal hydride complex of copper(I). This transformation was applied to conjugate reduction of alpha,beta-unsaturated compounds with a hydrosilane mediated by copper(I) chloride. (C) 1997 Elsevier Science Ltd.
  • M Hojo, H Harada, H Ito, A Hosomi
    CHEMICAL COMMUNICATIONS 21 2077 - 2078 1997年11月 [査読有り][通常論文]
     
    Tetrabutylmanganese ate complex 'Bu4MnLi2' reacts with allylic and prop-2-ynylic bromides to generate the corresponding allyl-and prop-2-ynyl-manganese species which further react with electrophiles such as aldehydes, ketones, epoxide and chlorosilanes to afford the corresponding allylated and prop-2-ynylated and/or allenylated products in high yields.
  • K Miura, T Hondo, H Saito, H Ito, A Hosomi
    JOURNAL OF ORGANIC CHEMISTRY 62 24 8292 - 8293 1997年11月 [査読有り][通常論文]
  • H Ito, K Arimoto, H Sensui, A Hosomi
    TETRAHEDRON LETTERS 38 22 3977 - 3980 1997年06月 [査読有り][通常論文]
     
    A first observation of the direct alkynyl group transfer from silicon to copper is reported. The silicon group of alkynylsilanes was smoothly replaced by copper (I) chloride in DMI to give the corresponding copper (I) acetylides. This transformation was applied to the synthesis of alkynyl ketones catalyzed by CuCl. (C) 1997 Elsevier Science Ltd.
  • M Hojo, H Harada, H Ito, A Hosomi
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 119 23 5459 - 5460 1997年06月 [査読有り][通常論文]
  • H Ito, H Sensui, K Arimoto, K Miura, A Hosomi
    CHEMISTRY LETTERS 7 639 - 640 1997年 [査読有り][通常論文]
     
    Copper(I) salt can be used as a promoter for the cross-coupling reactions between aryl- or heteroarylsilanes and aryl halides without a fluoride ion. Under these mild conditions, even a substrate containing a fluoride ion-sensitive silyloxyl group was employed directly.
  • M Hojo, H Aihara, H Ito, A Hosomi
    TETRAHEDRON LETTERS 37 51 9241 - 9244 1996年12月 [査読有り][通常論文]
     
    ''Tailor-made'' carbonyl ylides bearing only alkyl snbstituents or no substituents were efficiently generated from alpha-chloroalkyl alpha'-chloroalkyl ethers in the presence of samarium reagents. Using these novel and synthetically practical carbonyl ylides, optionally substituted and stereochemically defined tetrahydrofurans, dihydrofurans and dioxolane were synthesized in a single Step. Copyright (C) 1996 Elsevier Science Ltd
  • K Miura, M Funatsu, H Saito, H Ito, A Hosomi
    TETRAHEDRON LETTERS 37 50 9059 - 9062 1996年12月 [査読有り][通常論文]
     
    Low-valent titanium and zirconium reagents in situ prepared from metallocene dichlorides (Cp(2)MCl(2): M = Ti, Zr) and magnesium powder activated by 1,2-dibromoethane smoothly reacted with allyl propargyl ethers to afford 3-methylenetetrahydrofurans in good yields. It is noteworthy that the Cp(2)Zr- and Cp(2)Ti-mediated cyclizations proceed with inverse stereoselectivity. Copyright (C) 1996 Elsevier Science Ltd
  • K Miura, D Itoh, T Hondo, H Saito, H Ito, A Hosomi
    TETRAHEDRON LETTERS 37 47 8539 - 8542 1996年11月 [査読有り][通常論文]
     
    In the presence of AIBN, allylstannanes bearing an electron-withdrawing group at the beta-position easily reacted with terminal and electron-deficient internal alkynes to give beta-allylsubstituted vinylstannanes in moderate to good yields. The allylstannylation proceeds with anti addition exclusively. Copyright (C) 1996 Elsevier Science Ltd
  • K Miura, T Matsuda, T Hondo, H Ito, A Hosomi
    SYNLETT 1996 6 555 - & 1996年06月 [査読有り][通常論文]
     
    Allylstannanes bearing an electron-withdrawing group at the beta-position easily reacted with various electron-deficient alkenes to introduce both allyl and stannyl groups.
  • M Murakami, H Ito, Y Ito
    CHEMISTRY LETTERS 1 7 - 8 1996年 [査読有り][通常論文]
     
    The reaction of alkyllithium with 2,6-xylyl isocyanide led to the trimerization of the isocyanide to afford an indole derivative. The anomalous reaction pattern provided inference about the structural features of the intermediate organolithium species.
  • M Murakami, H Ito, Y Ito
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 69 1 25 - 30 1996年01月 [査読有り][通常論文]
     
    The preparation of (alkaneimidoyl)lanthanide(III) reagents and their reactions with carbonyl compounds were studied. Alkyllithium was added to a mixture of an anhydrous lanthanide salt and 2,6-xylyl isocyanide in tetrahydrofuran at -78 degrees C. Among a series of lanthanide salts, CeCl3 effected the quantitative conversion of the isocyanide to afford an orange solution of (alkaneimidoyl)cerium(III). Although LaCl3 SmI3, and Sm(OTf)(3) were found to be highly reactive, multiple insertion of the isocyanide ensued. (Alkaneimidoyl)cerium(III) could also be prepared by the reaction of dialkylmagnesium with CeCl3 and 2,6-xylyl isocyanide at -45 degrees C. The thus-prepared (alkaneimidoyl)cerium(III) reacted with a carbonyl compound to afford an addition product, i.e., an alpha-hydroxy imine. The present reactions for the preparation of (alkaneimidoyl)cerium(III) provide a convenient synthetic equivalent to a nucleophilic acyllanthanide species with a wide variation for the acyl group.
  • M Murakami, H Ito, Y Ito
    CHEMISTRY LETTERS 3 185 - 186 1996年 [査読有り][通常論文]
     
    Preparation of a C-13-labeled isocyanide and its application to the total synthesis of [2-C-13]D-ribo-C-18-phytosphingosine are described. The synthesis of the labeled phytosphingosine is based on the use of the isocyanide as a (CH)-C-13-NH2 precursor in the SmI2-mediated three-component coupling reaction, wherein regio- and stereoselective incorporation of a C-13 nuclide in the carbon skeleton is achieved.
  • M MURAKAMI, H ITO, Y ITO
    JOURNAL OF ORGANIC CHEMISTRY 58 24 6766 - 6770 1993年11月 [査読有り][通常論文]
     
    Preparation of an isocyanide having a removable N-substituent and its application to the stereoselective synthesis of 2-amino alcohols are described. 4-(tert-Butyldimethylsiloxy)-2,6-xylyl isocyanide was prepared from commercially available 3,5-xylenol. The isocyanide underwent a samarium iodide-mediated coupling reaction with organic halides and carbonyl compounds. Reduction of the reaction mixture with NaBH4 selectively afforded anti 2-(arylamino) alcohols, which were then deprotected to the corresponding 2-(primary amino) alcohols via desilylation with TBAF followed by oxidation with DDQ. A ceramide was successfully synthesized by use of the present stereoselective synthetic method for 2-amino alcohols, demonstrating a new synthetic utility of the isocyanide as an aminomethylene equivalent.
  • Murakami M, Kawano T, Ito H, Ito Y
    Journal of Organic Chemistry 58 6 1458 - 1465 1993年03月 [査読有り][通常論文]
     
    A new strategy for the synthesis of a-hydroxy ketones by samarium(II) iodide-mediated three-component coupling of organic halides, an isocyanide, and carbonyl compounds is disclosed. An (alpha-iminoalkyl)samarium(III) species is generated in situ by treatment of an organic halide with 2 equiv of samarium(II) iodide in the presence of 2,6-xylyl isocyanide. Subsequent treatment of the mixture with a carbonyl compound affords alpha-hydroxy imines, which are converted by acid-catalyzed hydrolysis to the corresponding alpha-hydroxy ketones. The mild reaction conditions employed are compatible with a variety of functionalities including terminal acetylenes and trimethylsilyl ethers. Application of the method to the synthesis of alpha-hydroxy aldehydes is also presented.
  • M MURAKAMI, H ITO, Y ITO
    JOURNAL OF ORGANIC CHEMISTRY 53 17 4158 - 4159 1988年08月 [査読有り][通常論文]

MISC

書籍等出版物

  • 錯体化学 基礎から応用まで (エキスパート応用化学テキストシリーズ)
    長谷川 靖哉, 伊藤 肇 
    講談社 2014年03月

講演・口頭発表等

所属学協会

  • 高分子学会   近畿化学協会   有機合成化学協会   アメリカ化学会   日本化学会   

共同研究・競争的資金等の研究課題

  • レドックスメカノケミストリーによる固体有機合成化学
    科学技術振興機構:戦略的創造研究推進事業
    研究期間 : 2019年10月 -2025年03月
  • 非対称稠密反応空間による不斉ホウ素化
    日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2018年04月 -2022年03月 
    代表者 : 伊藤 肇, 関 朋宏, 前田 理, 百合野 大雅
     
    本研究の目的の一つは、計算化学を援用することで、光学活性銅(I)触媒の合理的設計を行い、ロンドン分散力などの弱い相互作用をコントロールし、最終的には未踏の研究領域である「非対称稠密型触媒」を開発することである。本年度では、以下の成果を得た。 1. 末端アレンのホウ素化環化反応(Chem. Commun. 2018, 54, 4991):アルキルハライド部位を有するアレン基質に対して銅(I)触媒によるホウ素化を施すと、末端アレン選択的にホウ素化が進行し、生じるアルキル銅(I)中間体がアルキルハライド部位に環化反応下生成物が選択的に得られた。計算化学による反応機構解析を行った。 2. 脱フッ素化ホウ素化による光学活性アリルホウ素化合物の合成法開発(Angew. Chem. Int. Ed. 2018, 57, 7196): CF3基をもつE-アルケンに対して、光学活性銅(I)触媒によるホウ素化を実施すると、対応する1,1-ジフルオロ光学活性アリルホウ素化合物を高収率かつ高エナンチオ選択性で得た。 3. 量子化学計算主導デザインによる脂肪族末端アルケンの不斉ヒドロホウ素化(Nature Commun. 2018, 9, 2290): 実験結果をもとに遷移状態を計算・解析し触媒の設計原理を抽出、さらに実験を繰り返すことで高い選択性、活性をもつ触媒のデザインに成功した。今回開発した触媒は、C1対称性をもつ「非対称稠密型触媒」であり、これまでの配位子設計手法では到達し得ない、独自の構造を持つ。 4. アシルボラン化合物の高効率合成法の開発(Angew. Chem. Int. Ed. 2019, Just Accepted): 5. メカノケミストリーによるホウ素化反応の開発 (Nature Commun. 2019, 10, 111; Chem. Eur. J. 2019, 25, 4654)
  • ドミノ型相転移ソフトクリスタルの機構解明と新機能創成
    日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2017年06月 -2022年03月 
    代表者 : 伊藤 肇, 石山 竜生, 関 朋宏
     
    1. トリフェニルエテニル構造を持つアリール金イソシアニド錯体の結晶ジャンプ:独自の構造を持つトリフェニルエテニル金(4ークロロフェニルイソシアニド)錯体の合成を初めて行い、顕著な結晶ジャンプ現象を示すことを発見した。室温付近から-150℃まで温度を下げると結晶がジャンプする。単結晶X線構造解析と高速カメラなどによる解析を行い、分子レベルでのミクロな結晶構造変化と、マクロレベルでの結晶の形状変化の間での明確かつ異方的な相関を見出した。DSC測定および温度可変単結晶X線構造解析の結果から-50℃付近で相転移が起こっていることが明らかになった。温度変化に対する結晶の構造変化は異方的であり、ジャンプ時には結晶の表面に亀裂が入るが、これは構造が伸長するb軸と垂直の面に平行である。相転移時の結晶外形の伸長が、ジャンプする原因になっていると推察できた。 2. メカノケミストリーによる固体クロスカップリングの開発:有機合成反応は一般に溶媒を用いて実施することが必要で、反応剤だけを直接反応に用いることはほとんどない。特に反応剤が構造的に安定な固体の場合は、構造変化や反応が起こりにくいため、有効な反応系は限られていた。我々は、ドミノ型結晶相転移やメカノクロミズムに関する研究から、有機結晶の構造がかなり緩やかで反応性に富む可能性があることを見出していた。クロスカップリングは非常に有効な有機合成の手法であるが、固体に適用された例はほぼない。ある種の添加剤を用いると、有機溶媒を用いずに、固体状態で進行するクロスカップリング反応が実施可能であることを見出した。 3. 計算化学による結晶の安定性、発光及び相転移メカニズムの研究:分子動力学法によるドミノ型相転移挙動の解析と、QM/MM法による相転移前後における熱力学的な構造安定性、発光性の要因について検討を行った。
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 伊藤 肇
     
    有機ホウ素化合物は、鈴木カップリングなどの反応の重要な出発物質であり、有機合成化学において欠かすことのできない反応中間体である。また、有機材料として重要な化合物である。本研究では、過去に開発したシリルボラン/塩基反応系を拡張し、反応機構の解明並びに、ヘテロ芳香族有機ホウ素化合物・官能基をもつ芳香族有機ホウ素化合物のシリルボラン/塩基反応系による合成、トリアリール型有機ホウ素化合物の合成法の開発に成功した。
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2015年 -2017年 
    代表者 : 伊藤 肇
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2014年 -2014年 
    代表者 : 伊藤 肇
  • 文部科学省:科学研究費補助金(新学術領域研究(研究領域提案型))
    研究期間 : 2011年 -2011年 
    代表者 : 伊藤 肇
  • 文部科学省:科学研究費補助金(基盤研究(A))
    研究期間 : 2011年 -2011年 
    代表者 : 伊藤 肇
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2010年 -2010年 
    代表者 : 伊藤 肇
     
    本研究では、機械的刺激によりUV照射下でのフォトルミネッセンスが変化する化合物「メカノクロミック化合物」の単結晶の表面に、AFMなどを用いて微小な機械的刺激を与え、極小のピット(機械的な加工痕)を作成し、その発光性の変化の検出が可能であるかを検証することを目的として研究をおこなった。研究の第一段階として、我々がすでに報告しているメカノクロミック化合物に加えて、よりこの目的に適した化合物の合成、開発を検討した。すなわち機械的刺激に敏感かつ、小領域での刺激であっても明瞭な判別が可能なスペクトル変化を与える化合物の合成を行った。新たな一般的合成法の検討の結果、塩化金イソシアニド錯体に対して、アリール有機金属(リチウム、マグネシウム、亜鉛)を反応させることで、さまざまなアリール金(I)イソシアニド錯体が合成可能であることが明らかになた。また、それらのメカノメカノクロミズム特性を調べたところ、オリジナル錯体で観察された青から黄色への発光色の変化だけではなく、緑からオレンジなどの変化を示す化合物をデザインできることが明らかになった。これらの発光性メカノクロミック化合物の単結晶に対しAFM装置のカンチレバーを利用して、ミクロンからナノサイズの書き込み(機械的刺激)を行い、微小ピットを作成し、蛍光顕微鏡によるその発光性の変化の観察、SEMによる観察、AFMによる表面の観察を行った。その結果、微小な機械的ピットの作成(20×20ナノメートル)が可能であることがわかった。サブミクロンサイズの比較的大きなピットでは、ピットにおける発光性の変化が観察できた。
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2008年 -2010年 
    代表者 : 伊藤 肇
     
    不斉銅触媒を用いて光学活性ホウ素化合物を効率よく合成する方法を開発した。銅塩、不斉ホスフィン配位子からなる触媒系で、様々な基質を反応させると、対応する光学活性有機ホウ素化合物が高い効率で得られた。この新方法により、これまで不可能であった、光学活性シクロプロピルホウ素化合物、アリルホウ素化合物、ホモアリルホウ素化合物の触媒的不斉合成が可能になり、医薬中間体などの合成が容易となる。
  • 文部科学省:科学研究費補助金(特定領域研究)
    研究期間 : 2008年 -2009年 
    代表者 : 伊藤 肇
     
    本研究では、金(I)-イソシアニド錯体が、顕著な発光性メカノクロミズム特性を有していることを明らかにした。この錯体は乳鉢中ですりつぶすなどの機械的刺激により、そのフォトルミネッセンスが大きく変化する上、発光性が変化した錯体を溶媒にさらすことで、容易にもとの発光状態へ戻すことが可能である。また、この現象のメカニズムについて考察を行った。今年度は、メカノクロミズム特性を持つ化合物を水中に分散してできる有機ナノ結晶が、単価結晶状態、溶液状態とは大きく異なる発光特性を有することを明らかにした。また、単結晶にたいして、AFMを用いて刺激を加えることにより、ミクロサイズのスクラッチが形成でき、さらにこのスクラッチ痕が発光性の変化として観察できることを明らかにした。この化合物は、こする前の状態では青色発光を示す微結晶であり、これにすりつぶすという機械的刺激を加えることにより、アモルファス状態へと変化する性質を持つ。青色発光を示す微結晶では、π-πスタッキングによる分子間相互作用が支配的であるが、アモルファス状態では、おそらく、金原子間同士の弱い結合が形成され、これを介した分子間相互作用が支配的になると考えられる。溶媒を加えると再結晶がおこり、熱力学的に安定なもとの青色発光を示す状態に戻る。この現象は、配位子に含まれるフッ素原子の小さい分子間力により、分子同士のずれが起こりやすくなり、機械的刺激による固体相の変化が誘起されやすくなっていることが一つの要因であると推測される。熱分析などの結果からは、この機械的刺激によってもとの状態より高いエネルギー状態のメタ安定状態が形成されていることが示唆された。
  • 発光性メカノクロミックプローブの開発
    JST戦略的創造研究推進制度(個人研究型) (個人研究推進事業:さきがけ研究21‐PRESTO)
    研究期間 : 2008年
  • 文部科学省:科学研究費補助金(特定領域研究)
    研究期間 : 2007年 -2007年 
    代表者 : 伊藤 肇
     
    「発光性メカノクロミズム」とは、ある化合物に対して機械的刺激を与えたときに、その発光性が変化する性質のことである。このような性質を持つ化合物は、力学感知センサーや記録材料として幅広い応用が期待できる。しかし、この「発光性メカノクロミズム」特性をもつ化合物の合成例はごく限られていた。報告者は、金(I)錯体の多くが固体、室温でも強い発光性を示すことに着目して研究を行い、二核金(I)-イソシアニド錯体[(C_6F_5Au)_2(μ-1,4-diisocyanobenzene)](I)が、この発光性メカノクロミズム特性を有していることを明らかにした。この錯体は乳鉢中ですりつぶすなどの機械的刺激により、そのフォトルミネッセンスが大きく変化する上、発光性が変化した錯体を溶媒にさらすことで、容易にもとの発光状態へ戻すことが可能である。また、吸収スペクトル、発光スペクトル測定および、エックス線構造解析、粉末X線回折(PXRD)、IRなどからこの現象のメカニズムを考察した。金(I)錯体では、金同士の弱い相互作用が形成される場合があり、その結果特徴的な発光性を示すことが知られている。この錯体の場合、機械的刺激で、金(I)原子間の相互作用が誘起されるものと考えられる。金(I)錯体の中でも、特にこの錯体がメカノクロミズムを示す理由については、今後詳細な研究が必要となるが、配位子に含まれるフッ素原子の小さい分子間力により、分子同士のずれが起こりやすくなり、機械的刺激による固体相の変化が誘起されやすくなっていることが一つの要因であると推測される。
  • 文部科学省:科学研究費補助金(基盤研究(C))
    研究期間 : 2006年 -2007年 
    代表者 : 伊藤 肇
     
    光学活性化合物の効率のよい合成は重要な課題である。加えて最近では、資源の有効利用や廃棄物の低減につながる新しい合成反応の重要性が高まっている。本研究では、光学活性金(1)錯体触媒を用いた脱水素シリル化による速度論的光学分割という新しい手法で、光学活性化合物を効率よく合成し、かつ廃棄物が少ない方法の開発を検討した。その結果、光学活性金錯体触媒を用いたアルコールのヒドロシランによる脱水素シリル化反応において、不斉誘起が起こることを初めて明らかにした。まず予備的実験として、Xantphosタイプの配位子を数種類合成し、金(1)錯体を作成してその触媒活性の比較を行った。次に、各種光学活性ホスフィン配位子を用いて速度論的光学分割を検討した。金属ヒドリドは、合成反応剤や、触媒反応中間体としてよく知られており、様々な金属に対応する金属ヒドリドが合成されている。しかし、この触媒反応の重要な反応中間体として予想されていた金ヒドリド錯体はこれまで合成、単離された例がなく、その構造や性質については長らく未知であった。この金錯体触媒による光学活性化合物の合成研究を進展させていく中で、この脱水素シリル化反応において、金-ヒドリド錯体が反応中間体として実際に生じることを見いだし、このNMRスペクトル観察、Mass spectrometry測定を行い、構造解析に成功した。本研究は、金錯体の不斉合成への利用という応用面と、これまでに未知の化学種であった金ヒドリド錯体の合成という二つの成果を得た。今後、この二つを組み合わせることにより、光学活性金ヒドリド錯体の合成と、これを利用して高い不斉収率を与える触媒反応の開発への足がかりが得られた。
  • 文部科学省:科学研究費補助金(特定領域研究(A))
    研究期間 : 2000年 -2001年 
    代表者 : 伊藤 肇, 永田 央, 永田 央, 伊藤 肇
     
    後周期遷移金属化合物を触媒とする反応は、有機合成化学的に非常に有用であり、これまで多くの実験的研究が行われている。また、その反応機構を知ることは、触媒反応の設計上重要なことから、計算科学的な研究も非常に盛んである。われわれは、最近、11族金属を触媒とする有機合成反応を新たに開発し、成果を上げている。その一連の研究の中で、金(I)錯体を用いたヒドロシリル化反応を発見した。金(I)錯体は、後周期遷移金属からなる錯体でありながら、有機合成反応の触媒として使われた例は非常に少なかった。最近、われわれが発見した例を含めて、金錯体触媒が、有用な触媒として働くこと例が報告されている。しかしこれまで、金錯体を用いた触媒反応を計算化学的に考察した例はない。われわれは、自分たちが発見した金(I)錯体の触媒反応の計算化学的研究を行い、その結果、金(I)錯体を用いる触媒反応に対する有益な知見を得た。金ヒドリド錯体、アルデヒド、ヒドロシランの出発系から比較して遷移状態Aの活性化エネルギーは+15.8kcal/molであった。この付加反応のあと、金アルコキシド錯体が形成されるが、その生成エネルギーは原系に対して26.1kcal/mol安定である。次の金アルコキシド錯体とヒドロシランの反応の遷移状態Bは原系に対して-16.5kcal/mol安定であり、反応前の金アルコキシド錯体とヒドロシランからの活性化エネルギーは+9.6kcal/molとなる。この反応の結果、原料であるアルデヒドがヒドロシリル化されたシリルエーテルが生成し、同時に触媒活性種である金ヒドリド錯体が再生し触媒サイクルが一巡する。この触媒1サイクルに伴う全生成エネルギーは50.1kcal/molである。これまで実験的な研究例が少なかった金(I)錯体の触媒反応について、始めて計算化学的な考察を行った。金(I)錯体を用いた触媒反応の研究はようやく始まったばかりであり、今回の反応も含めて、反応機構の研究は少ない。触媒反応に関する過去の蓄積が金(I)錯体ではあまりなく、また他の反応に参考を求めることができない今回のような反応では、金(I)錯体が、この反応の途中でどのような中間体・遷移状態をとり、どのようなエネルギー変化を取りながら触媒サイクルが進行するかは、計算化学の方法を用いることで始めてわかることであった。今回得られた成果は、さらに高度な反応の設計に役に立つことが予想できる。
  • 文部科学省:科学研究費補助金(奨励研究(A))
    研究期間 : 1999年 -2000年 
    代表者 : 伊藤 肇
     
    後周期遷移金属化合物と有機ケイ素化合物との組み合わせにより,これまで多くの有用な有機合成反応が開発されている。例えば,ヒドロシランなどの有機ケイ素化合物は8,9,10族などの後周期遷移金属化合物に対する反応が知られており,これを利用してヒドロシリル化などの触媒的合成反応が数多く開発されてきた。しかし,銅(I)塩などの11族金属化合物と有機ケイ素化合物の反応例は少なく,これらを触媒とする合成反応の研究も限られていた。我々は最近、ヒドロシランやジシランのような有機ケイ素化合物を用い、銅(I)塩を触媒とする有用な合成反応を見いだした。さらに、銅(I)塩触媒による、有機ホウ素化合物を用いた触媒反応の開発もおこなった。また,同じ11族金属化合物である金(I)錯体を用いた触媒反応の開発にも成功し,これまで極めて例の少なかった金(I)錯体による触媒反応の新しい設計指針が得られた。Si-Si結合を持つ化合物と銅(I)塩との反応:銅(I)塩によりジシランが切断されることを初めて発見し、銅(I)塩触媒を用いたジシランによるα,β-エノンの共役シリル化反応を開発した。類似の反応は、過去にPd,Ni触媒でも報告されているが、銅(I)触媒を用いたこの反応は、ジシランに対する反応活性がより高く、合成反応としての一般性に優れている。(b)Si-H結合を持つ化合物と銅(I)塩の反応:ヒドロシランと銅(I)塩がDMI中で反応することを初めて明らかにした。さらにこれを利用してα,β-不飽和カルボニル化合物の選択的1,4-還元反応を開発した。
  • 文部科学省:科学研究費補助金(奨励研究(A))
    研究期間 : 1997年 -1998年 
    代表者 : 伊藤 肇
     
    1. シリルエノールエーテルの銅(I)塩による選択的アシル化:ケイ素・銅交換反応がシリルエノールエーテル上でも進行することを利用して,シリルエノールエーテルの銅(I)塩による選択的O-アシル化を行ったところ,広範な基質に対して良好な収率で目的物が得られた.2. 銅(I)触媒によるα,β一不飽和力ルボニル化合物の求核的シリル化:ケイ素求核剤はクロロシランやジシランからアルカリ金属を用いて還元するなどの方法で発生することができるが,炭素求核剤と比べると比較的発生させにくいことからやや敬遠されがちであった.われわれはケイ素-ケイ素結合が銅(I)塩で切断されることを初めて発見し,これを利用して求核的なケイ素化剤を触媒的に発生させる方法を見つけた.1〜10%触媒量のCU(I)OTfの存在下,ジシランがα,β-不飽和カルボニル化合物に1,4-付加反応し,引き続く酸加水分解により,β-シリル化体が高収率で得られることを新たに見いだした.この反応は銅塩に対する配位子の効果が顕著で,銅(I)塩に対して小過剰のトリブチルホスフィンの添加により収率が向上する.また溶媒としてはDMFがもっともよい結果を与える.基質としてはα,β-不飽和アルデヒドも可能であるが,α,β-不飽和エステルの場合は収率が低下する.ジシランのα,β-不飽和ケトンへの1,4-付加反応はPd触媒を用いた報告があるが,ハロゲン置換により活性化されたジシランが必要であるなど制限があり,この銅(I)塩触媒を用いる方法の方が一般性は高い.3. 光学活性ヒドロシランにおけるケイ素・銅(I)交換:光学活性ヒドロシランにおいて,ケイ素・銅(I)交換反応に基づくシリルエーテル合成を行ったところ,極性溶媒中にもかかわらず,ケイ素上の立体が保持された生成物が得られた.このことはこのケイ素・銅交換反応を経由する反応機構の考察に有益な示唆を与える.
  • 高活性銅(I)錯体触媒の開発 有機ナノ構造体の合成
  • Development of Highly active Cu(I) catalysts Synthesis of organic nano-structure


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